Remove unused CSS

app/assets/stylesheets/pages/diff.scss

@@ -9,31 +9,6 @@
     font-weight: 400;
   }
-  .diff-header {
-    position: relative;
-    background: $gray-light;
-    border-bottom: 1px solid $border-color;
-    padding: 10px 16px;
-    color: $gl-text-color;
-    z-index: 10;
-    border-radius: 3px 3px 0 0;
-
-    .diff-title {
-      font-family: $monospace_font;
-      word-break: break-all;
-      display: block;
-
-      .file-mode {
-        color: $file-mode-changed;
-      }
-    }
-
-    .commit-short-id {
-      font-family: $monospace_font;
-      font-size: smaller;
-    }
-  }
-
   .file-title,
   .file-title-flex-parent {
     cursor: pointer;

app/assets/stylesheets/pages/notes.scss

@@ -284,10 +284,6 @@ ul.notes {
     }
   }
-  .diff-header > span {
-    margin-right: 10px;
-  }
-
   .line_content {
     white-space: pre-wrap;
   }