Fix Giphy link previews

SignalServiceKit/src/Messages/Interactions/OWSLinkPreview.swift

@@ -340,7 +340,6 @@ public class OWSLinkPreview: MTLModel {
         "media2.giphy.com",
         "media3.giphy.com",
         "gph.is"
-        
     ]
 
     // For media domains, we DO NOT require an exact match - subdomains are allowed.

SignalServiceKit/src/Util/MIMETypeUtil.m

@@ -89,6 +89,7 @@ NSString *const kSyncMessageFileExtension = @"bin";
             @"image/x-tiff" : @"tif",
             @"image/bmp" : @"bmp",
             @"image/x-windows-bmp" : @"bmp",
+            @"image/gif" : @"gif"
         };
     });
     return result;