fix selector mismatch on emoji images

Author: silverwind

web_src/css/repo.css

@@ -1823,16 +1823,12 @@
   clear: right;
 }
 
-.repository .diff-file-box.file-content img {
+.repository .diff-file-box.file-content .image-diff img {
   max-width: 100%;
   padding: 0;
   border-radius: 0;
 }
 
-.repository .diff-file-box.file-content img.emoji {
-  padding: 0;
-}
-
 .repository .diff-file-box .ui.bottom.attached.table.segment {
   padding-top: 5px;
   padding-bottom: 5px;