Merge branch '24673-broken-test-in-merge_request_widget_spec-js' into 'master'

Fix broken merge request widget spec

## What does this MR do?
Converts the invalid es6 syntax of the merge_request_widget_spec which is actually causing the spec not to run through teaspoon

## Are there points in the code the reviewer needs to double check?
None

## Why was this MR needed?
Get specs working again

## Screenshots (if relevant)
None

## Does this MR meet the acceptance criteria?

- [ ] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?
Closes #24673

See merge request !7594

spec/javascripts/merge_request_widget_spec.js

@@ -35,9 +35,9 @@
           external_url_formatted: 'test-url.com'
         }];
 
-        spyOn(jQuery, 'getJSON').and.callFake((req, cb) => {
+        spyOn(jQuery, 'getJSON').and.callFake(function(req, cb) {
           cb(this.ciEnvironmentsStatusData);
-        });
+        }.bind(this));
       });
 
       it('should call renderEnvironments when the environments property is set', function() {