remove unused methods

src/ImageSharp/Image/ImageBase{TPixel}.cs

@@ -271,14 +271,6 @@ namespace SixLabors.ImageSharp
             this.Configuration = other.Configuration;
         }
 
-        /// <summary>
-        /// Releases any unmanaged resources from the inheriting class.
-        /// </summary>
-        protected virtual void ReleaseUnmanagedResources()
-        {
-            // TODO release unmanaged resources here
-        }
-
         /// <summary>
         /// Disposes the object and frees resources for the Garbage Collector.
         /// </summary>
@@ -290,8 +282,6 @@ namespace SixLabors.ImageSharp
                 return;
             }
 
-            this.ReleaseUnmanagedResources();
-
             if (disposing)
             {
                 this.ReturnPixels();