[11.9] Revert "Remove HipChat integration from GitLab"

See merge request gitlab-org/gitlab-ce!27257

+ address small nitpicks

I've followed the [upgrade guide](https://github.com/thoughtbot/factory_bot/blob/4-9-0-stable/UPGRADE_FROM_FACTORY_GIRL.md

) and ran these two commands:

```
grep -e FactoryGirl **/*.rake **/*.rb -s -l | xargs sed -i "" "s|FactoryGirl|FactoryBot|"
grep -e factory_girl **/*.rake **/*.rb -s -l | xargs sed -i "" "s|factory_girl|factory_bot|"
```

Signed-off-by: Rémy Coutable <remy@rymai.me>

It was broken, because we introduced a default namespace, which was not used by terminal methods.

Use the EnforcedStyleForMultiline: no_comma option.

Signed-off-by: Rémy Coutable <remy@rymai.me>

The `ReferenceExtractor` would return an array of `ExternalIssue`
objects, and then perform `Array#-` to remove the issues
closed. `ExternalIssue`s had `==` defined, but not `hash` or `eql?`,
which are used by `Array#-`.