Remove NotNull guaurds on structs

src/ImageSharp/ColorSpaces/Conversion/Implementation/CieLab/CieLabToCieXyzConverter.cs

@@ -15,8 +15,6 @@ namespace SixLabors.ImageSharp.ColorSpaces.Conversion.Implementation.CieLabColor
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public CieXyz Convert(CieLab input)
         {
-            DebugGuard.NotNull(input, nameof(input));
-
             // Conversion algorithm described here: http://www.brucelindbloom.com/index.html?Eqn_Lab_to_XYZ.html
             float l = input.L, a = input.A, b = input.B;
             float fy = (l + 16) / 116F;

src/ImageSharp/ColorSpaces/Conversion/Implementation/CieLab/CieXyzToCieLabConverter.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Runtime.CompilerServices;
-using SixLabors.ImageSharp.ColorSpaces;
 
 namespace SixLabors.ImageSharp.ColorSpaces.Conversion.Implementation.CieLabColorSapce
 {
@@ -44,8 +43,6 @@ namespace SixLabors.ImageSharp.ColorSpaces.Conversion.Implementation.CieLabColor
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public CieLab Convert(CieXyz input)
         {
-            DebugGuard.NotNull(input, nameof(input));
-
             // Conversion algorithm described here: http://www.brucelindbloom.com/index.html?Eqn_XYZ_to_Lab.html
             float wx = this.LabWhitePoint.X, wy = this.LabWhitePoint.Y, wz = this.LabWhitePoint.Z;
 

src/ImageSharp/ColorSpaces/Conversion/Implementation/CieLch/CIeLchToCieLabConverter.cs

@@ -16,8 +16,6 @@ namespace SixLabors.ImageSharp.ColorSpaces.Conversion.Implementation.CieLchColor
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public CieLab Convert(CieLch input)
         {
-            DebugGuard.NotNull(input, nameof(input));
-
             // Conversion algorithm described here:
             // https://en.wikipedia.org/wiki/Lab_color_space#Cylindrical_representation:_CIELCh_or_CIEHLC
             float l = input.L, c = input.C, hDegrees = input.H;

src/ImageSharp/ColorSpaces/Conversion/Implementation/CieLch/CieLabToCieLchConverter.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Runtime.CompilerServices;
-using SixLabors.ImageSharp.ColorSpaces;
 
 namespace SixLabors.ImageSharp.ColorSpaces.Conversion.Implementation.CieLchColorSapce
 {
@@ -16,8 +15,6 @@ namespace SixLabors.ImageSharp.ColorSpaces.Conversion.Implementation.CieLchColor
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public CieLch Convert(CieLab input)
         {
-            DebugGuard.NotNull(input, nameof(input));
-
             // Conversion algorithm described here:
             // https://en.wikipedia.org/wiki/Lab_color_space#Cylindrical_representation:_CIELCh_or_CIEHLC
             float l = input.L, a = input.A, b = input.B;

src/ImageSharp/ColorSpaces/Conversion/Implementation/CieLchuv/CieLchuvToCieLuvConverter.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Runtime.CompilerServices;
-using SixLabors.ImageSharp.ColorSpaces;
 
 namespace SixLabors.ImageSharp.ColorSpaces.Conversion.Implementation.CieLchuvColorSapce
 {
@@ -16,8 +15,6 @@ namespace SixLabors.ImageSharp.ColorSpaces.Conversion.Implementation.CieLchuvCol
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public CieLuv Convert(CieLchuv input)
         {
-            DebugGuard.NotNull(input, nameof(input));
-
             // Conversion algorithm described here:
             // https://en.wikipedia.org/wiki/CIELUV#Cylindrical_representation_.28CIELCH.29
             float l = input.L, c = input.C, hDegrees = input.H;

src/ImageSharp/ColorSpaces/Conversion/Implementation/CieLchuv/CieLuvToCieLchuvConverter.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Runtime.CompilerServices;
-using SixLabors.ImageSharp.ColorSpaces;
 
 namespace SixLabors.ImageSharp.ColorSpaces.Conversion.Implementation.CieLchuvColorSapce
 {
@@ -16,8 +15,6 @@ namespace SixLabors.ImageSharp.ColorSpaces.Conversion.Implementation.CieLchuvCol
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public CieLchuv Convert(CieLuv input)
         {
-            DebugGuard.NotNull(input, nameof(input));
-
             // Conversion algorithm described here:
             // https://en.wikipedia.org/wiki/CIELUV#Cylindrical_representation_.28CIELCH.29
             float l = input.L, a = input.U, b = input.V;

src/ImageSharp/ColorSpaces/Conversion/Implementation/CieLuv/CieLuvToCieXyzConverter.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Runtime.CompilerServices;
-using SixLabors.ImageSharp.ColorSpaces;
 
 namespace SixLabors.ImageSharp.ColorSpaces.Conversion.Implementation.CieLuvColorSapce
 {
@@ -16,8 +15,6 @@ namespace SixLabors.ImageSharp.ColorSpaces.Conversion.Implementation.CieLuvColor
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public CieXyz Convert(CieLuv input)
         {
-            DebugGuard.NotNull(input, nameof(input));
-
             // Conversion algorithm described here: http://www.brucelindbloom.com/index.html?Eqn_Luv_to_XYZ.html
             float l = input.L, u = input.U, v = input.V;