Add comment about why we need to stop parsing JSON

Fix
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/12198#note_37146815

See https://gitlab.slack.com/archives/C0GQHHPGW/p1501779964878178

app/assets/javascripts/repo/services/repo_service.js

@@ -22,6 +22,7 @@ const RepoService = {
 
   getRaw(url) {
     return axios.get(url, {
+      // Stop Axios from parsing a JSON file into a JS object
       transformResponse: [res => res],
     });
   },