Remove remaining AsciiEncoding fields

src/ImageSharp/MetaData/Profiles/ICC/DataWriter/IccDataWriter.Primitives.cs

@@ -178,7 +178,7 @@ namespace SixLabors.ImageSharp.MetaData.Profiles.Icc
                 return 0;
             }
 
-            byte[] data = AsciiEncoding.GetBytes(value);
+            byte[] data = Encoding.ASCII.GetBytes(value);
             this.dataStream.Write(data, 0, data.Length);
             return data.Length;
         }
@@ -215,7 +215,7 @@ namespace SixLabors.ImageSharp.MetaData.Profiles.Icc
 
             value = value.Substring(0, Math.Min(length - lengthAdjust, value.Length));
 
-            byte[] textData = AsciiEncoding.GetBytes(value);
+            byte[] textData = Encoding.ASCII.GetBytes(value);
             int actualLength = Math.Min(length - lengthAdjust, textData.Length);
             this.dataStream.Write(textData, 0, actualLength);
             for (int i = 0; i < length - actualLength; i++)

src/ImageSharp/MetaData/Profiles/ICC/DataWriter/IccDataWriter.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.IO;
-using System.Text;
 
 namespace SixLabors.ImageSharp.MetaData.Profiles.Icc
 {
@@ -13,7 +12,6 @@ namespace SixLabors.ImageSharp.MetaData.Profiles.Icc
     internal sealed partial class IccDataWriter : IDisposable
     {
         private static readonly bool IsLittleEndian = BitConverter.IsLittleEndian;
-        private static readonly Encoding AsciiEncoding = Encoding.ASCII;
 
         /// <summary>
         /// The underlying stream where the data is written to

src/ImageSharp/MetaData/Profiles/ICC/TagDataEntries/IccDataTagDataEntry.cs

@@ -12,8 +12,6 @@ namespace SixLabors.ImageSharp.MetaData.Profiles.Icc
     /// </summary>
     internal sealed class IccDataTagDataEntry : IccTagDataEntry, IEquatable<IccDataTagDataEntry>
     {
-        private static readonly Encoding AsciiEncoding = Encoding.ASCII;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="IccDataTagDataEntry"/> class.
         /// </summary>
@@ -60,7 +58,7 @@ namespace SixLabors.ImageSharp.MetaData.Profiles.Icc
         /// Gets the <see cref="Data"/> decoded as 7bit ASCII.
         /// If <see cref="IsAscii"/> is false, returns null
         /// </summary>
-        public string AsciiString => this.IsAscii ? AsciiEncoding.GetString(this.Data, 0, this.Data.Length) : null;
+        public string AsciiString => this.IsAscii ? Encoding.ASCII.GetString(this.Data, 0, this.Data.Length) : null;
 
         /// <inheritdoc/>
         public override bool Equals(IccTagDataEntry other)