Merge branch 'remove-empty-describe' into 'master'

Remove empty describe block on key spec model

## What does this MR do?
Removes unnecessary describe in test

## Are there points in the code the reviewer needs to double check?
No

## Why was this MR needed?
It describe block not needed.

## Screenshots (if relevant)
No

## Does this MR meet the acceptance criteria?

- n/a [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- n/a [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- n/a API support added
- Tests
  - n/a Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] 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?
No

See merge request !6793

spec/models/key_spec.rb

@@ -5,9 +5,6 @@ describe Key, models: true do
     it { is_expected.to belong_to(:user) }
   end
 
-  describe "Mass assignment" do
-  end
-
   describe "Validation" do
     it { is_expected.to validate_presence_of(:title) }
     it { is_expected.to validate_presence_of(:key) }