Fix image banding that can sometimes show in high-res images.

app/src/main/java/org/thoughtcrime/securesms/components/subsampling/AttachmentRegionDecoder.java

@@ -52,7 +52,7 @@ public class AttachmentRegionDecoder implements ImageRegionDecoder {
     synchronized(this) {
       BitmapFactory.Options options = new BitmapFactory.Options();
       options.inSampleSize      = sampleSize;
-      options.inPreferredConfig = Bitmap.Config.RGB_565;
+      options.inPreferredConfig = Bitmap.Config.ARGB_8888;
 
       Bitmap bitmap = bitmapRegionDecoder.decodeRegion(rect, options);