Docs: Fix improperly declared code block

What does this MR do?

!29381 (merged) passed linting tests (how?) but it introduced a docs-lint error:

 => Linting prose...
  doc/ci/pipelines/settings.md
  308:1  error  Syntax highlighting hint        gitlab.CodeblockFences 
                "```text" must be one of:                              
                yaml, ruby, plaintext,                                 
                markdown, javascript, shell,                           
                golang, python, dockerfile, or                         
                typescript.                                            
 ✖ 1 error, 0 warnings and 0 suggestions in 1423 files.

which @sselhorn caught in !33395 (merged) - this MR fixes the issue.

Related issues

Author's checklist (required)

• Follow the Documentation Guidelines and Style Guide.
• If you have developer access or higher (for example, GitLab team members or Core Team members)
  • Apply the documentation label, plus:
    • The corresponding DevOps stage and group label, if applicable.
    • development guidelines when changing docs under doc/development/*, CONTRIBUTING.md, or README.md.
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  • Assign the designated Technical Writer.

When applicable:

• Update the permissions table.
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• Add the product tier badge.
• Add/update the feature flag section.
• If you're changing document headings, search doc/*, app/views/*, and ee/app/views/* for old headings replacing with the new ones to avoid broken anchors.

Review checklist

All reviewers can help ensure accuracy, clarity, completeness, and adherence to the Documentation Guidelines and Style Guide.

1. Primary Reviewer

• Review by a code reviewer or other selected colleague to confirm accuracy, clarity, and completeness. This can be skipped for minor fixes without substantive content changes.

2. Technical Writer

• Optional: Technical writer review. If not requested for this MR, must be scheduled post-merge. To request for this MR, assign the writer listed for the applicable DevOps stage.
  • Add Technical Writing and docs:: workflow label.
  • Add docs-only when the only files changed are under doc/*.

3. Maintainer

1. Review by assigned maintainer, who can always request/require the above reviews. Maintainer's review can occur before or after a technical writer review.
2. Ensure a release milestone is set.
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