show highlighted code correctly inside issue body

app/assets/stylesheets/gitlab_bootstrap/blocks.scss

@@ -34,13 +34,6 @@
     padding: 15px;
     word-wrap: break-word;
-    pre {
-      background: none !important;
-      margin: 0;
-      border: none;
-      padding: 0;
-    }
-
     .clearfix {
       margin: 0;
     }