Merge branch 'enable-scss-lint-space-after-variable-colon' into 'master'

Enable SpaceAfterVariableColon in scss-lint

## What does this MR do?
Enables `SpaceAfterVariableColon` in `.scss-lint.yml`

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

## Why was this MR needed?
Improve SCSS maintainability and consistency

## Screenshots (if relevant)
None

## Does this MR meet the acceptance criteria?

- Tests
  - [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)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?
#23485

See merge request !7080

.scss-lint.yml

@@ -191,7 +191,7 @@ linters:
   # Variables should be formatted with a single space separating the colon
   # from the variable's value.
   SpaceAfterVariableColon:
-    enabled: false
+    enabled: true
 
   # Variables should be formatted with no space between the name and the
   # colon.