Revert "GIF frames are of ImageType GIF"

This reverts commit af848c4.

Author: pkjuak

io/src/main/java/com/itextpdf/io/image/GifImageHelper.java

@@ -303,7 +303,7 @@ private static void readFrame(GifParameters gif) throws java.io.IOException {
             colorspace[3] = PdfEncodings.convertToString(gif.m_curr_table, null);
             Map<String, Object> ad = new HashMap<>();
             ad.put("ColorSpace", colorspace);
-            RawImageData img = new RawImageData(gif.m_out, ImageType.GIF);
+            RawImageData img = new RawImageData(gif.m_out, ImageType.NONE);
             RawImageHelper.updateRawImageParameters(img, gif.iw, gif.ih, 1, gif.m_bpc, gif.m_out);
             RawImageHelper.updateImageAttributes(img, ad);
             gif.image.addFrame(img);