Remove empty lines and unused using statements

src/ImageSharp/Formats/Png/IPngDecoderOptions.cs

@@ -1,11 +1,7 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
-using System;
-using System.Collections.Generic;
-using System.IO;
 using System.Text;
-using SixLabors.ImageSharp.PixelFormats;
 
 namespace SixLabors.ImageSharp.Formats.Png
 {

src/ImageSharp/Formats/Png/Zlib/Adler32.cs

@@ -78,10 +78,7 @@ namespace SixLabors.ImageSharp.Formats.Png.Zlib
         public long Value
         {
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            get
-            {
-                return this.checksum;
-            }
+            get => this.checksum;
         }
 
         /// <inheritdoc/>

src/ImageSharp/Formats/Png/Zlib/IChecksum.cs

@@ -17,10 +17,7 @@ namespace SixLabors.ImageSharp.Formats.Png.Zlib
         /// <summary>
         /// Gets the data checksum computed so far.
         /// </summary>
-        long Value
-        {
-            get;
-        }
+        long Value { get; }
 
         /// <summary>
         /// Resets the data checksum as if no update was ever called.