Fix improperly declared code block

Change from 'text' to 'plaintext'

doc/ci/pipelines/settings.md

@@ -305,7 +305,7 @@ https://example.gitlab.com/<namespace>/<project>/badges/<branch>/coverage.svg?st
 
 The text for a badge can be customized. This can be useful to differentiate between multiple coverage jobs that run in the same pipeline. Customize the badge text and width by adding the `key_text=custom_text` and `key_width=custom_key_width` parameters to the URL:
 
-```text
+```plaintext
 https://gitlab.com/gitlab-org/gitlab-foss/badges/master/coverage.svg?job=karma&key_text=Frontend+Coverage&key_width=100
 ```