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

So that whenever this failed:

    expect(response).to have_gitlab_http_status(200)

We see what's the response there. Here's an example:

```
1) API::Settings Settings PUT /application/settings custom repository storage type set in the config updates application settings
   Failure/Error: expect(response).to have_gitlab_http_status(200)
     expected the response to have status code 200 but it was 400. The response was: {"error":"password_authentication_enabled, signin_enabled are mutually exclusive"}
```

Removed all the unnecessary include of `WaitForAjax` and `ApiHelpers` in the specs.
Removed unnecessary usage of `api:true`

Restore changes for api spec files

Fix error in rspec Users

Delete extra space Repositories-spec