Remove dead code from ide.scss

1. .file-content has no img, .isZoomable, .isZoomed
2. There is no .multi-file-discard-btn anymore

app/assets/stylesheets/page_bundles/ide.scss

@@ -332,23 +332,6 @@ $ide-commit-header-height: 48px;
       padding: $gl-padding;
       max-width: 100%;
       max-height: 100%;
-
-      img {
-        max-width: 90%;
-      }
-
-      .isZoomable {
-        cursor: pointer;
-        cursor: zoom-in;
-
-        &.isZoomed {
-          cursor: pointer;
-          cursor: zoom-out;
-          max-width: none;
-          max-height: none;
-          margin-right: $gl-padding;
-        }
-      }
     }
 
     .file-info {
@@ -564,12 +547,6 @@ $ide-commit-header-height: 48px;
     background: $gray-100;
 
     outline: 0;
-
-    .multi-file-discard-btn {
-      > .btn {
-        display: flex;
-      }
-    }
   }
 
   &:active {
@@ -596,18 +573,6 @@ $ide-commit-header-height: 48px;
   }
 }
 
-.multi-file-discard-btn {
-  > .btn {
-    display: none;
-    width: $ide-commit-row-height;
-    height: $ide-commit-row-height;
-  }
-
-  svg {
-    top: 0;
-  }
-}
-
 .multi-file-commit-form {
   position: relative;
   background-color: $white-light;