Merge branch '21471-bold-text-in-ci-build-output-not-styled' into 'master'

Added `.term-bold` declaration.

## What does this MR do?

Added `.term-bold` declaration.

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

https://gitlab.com/gitlab-org/gitlab-ce/issues/21471#note_14874299

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry 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 you do - 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 #21471

See merge request !6171

app/assets/stylesheets/pages/xterm.scss

@@ -20,6 +20,9 @@
   $l-cyan: #8abeb7;
   $l-white: $ci-text-color;
 
+  .term-bold {
+    font-weight: bold;
+  }
   .term-italic {
     font-style: italic;
   }