Removed unused methods, added new throw helper method

src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs

@@ -1033,13 +1033,13 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
                 // Validate: 1-4 range
                 if (h is < 1 or > 4)
                 {
-                    JpegThrowHelper.ThrowInvalidImageContentException($"Bad horizontal sampling factor: {h}");
+                    JpegThrowHelper.ThrowBadSampling(h);
                 }
 
                 // Validate: 1-4 range
                 if (v is < 1 or > 4)
                 {
-                    JpegThrowHelper.ThrowInvalidImageContentException($"Bad vertical sampling factor: {v}");
+                    JpegThrowHelper.ThrowBadSampling(v);
                 }
 
                 if (maxH < h)

src/ImageSharp/Formats/Jpeg/JpegThrowHelper.cs

@@ -22,23 +22,6 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         [MethodImpl(InliningOptions.ColdPath)]
         public static void ThrowInvalidImageContentException(string errorMessage) => throw new InvalidImageContentException(errorMessage);
 
-        /// <summary>
-        /// Cold path optimization for throwing <see cref="InvalidImageContentException"/>'s.
-        /// </summary>
-        /// <param name="errorMessage">The error message for the exception.</param>
-        /// <param name="innerException">The exception that is the cause of the current exception, or a null reference
-        /// if no inner exception is specified.</param>
-        [MethodImpl(InliningOptions.ColdPath)]
-        public static void ThrowInvalidImageContentException(string errorMessage, Exception innerException) => throw new InvalidImageContentException(errorMessage, innerException);
-
-        /// <summary>
-        /// Cold path optimization for throwing <see cref="NotImplementedException"/>'s
-        /// </summary>
-        /// <param name="errorMessage">The error message for the exception.</param>
-        [MethodImpl(InliningOptions.ColdPath)]
-        public static void ThrowNotImplementedException(string errorMessage)
-            => throw new NotImplementedException(errorMessage);
-
         [MethodImpl(InliningOptions.ColdPath)]
         public static void ThrowBadMarker(string marker, int length) => throw new InvalidImageContentException($"Marker {marker} has bad length {length}.");
 
@@ -51,6 +34,9 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         [MethodImpl(InliningOptions.ColdPath)]
         public static void ThrowBadSampling() => throw new InvalidImageContentException("Bad sampling factor.");
 
+        [MethodImpl(InliningOptions.ColdPath)]
+        public static void ThrowBadSampling(int factor) => throw new InvalidImageContentException($"Bad sampling factor: {factor}");
+
         [MethodImpl(InliningOptions.ColdPath)]
         public static void ThrowBadProgressiveScan(int ss, int se, int ah, int al) => throw new InvalidImageContentException($"Invalid progressive parameters Ss={ss} Se={se} Ah={ah} Al={al}.");