ci: codeql: add the language to the category

[kmk3]

For consistency with the auto-generated yaml:

- name: Perform CodeQL Analysis
  uses: github/codeql-action/analyze@v3
  with:
    category: "/language:${{matrix.language}}"

Documentation:

• https://docs.github.com/en/code-security/code-scanning/creating-an-advanced-setup-for-code-scanning/customizing-your-advanced-setup-for-code-scanning#changing-the-languages-that-are-analyzed
• https://docs.github.com/en/code-security/code-scanning/creating-an-advanced-setup-for-code-scanning/customizing-your-advanced-setup-for-code-scanning#configuring-a-category-for-the-analysis

[github-advanced-security]

This pull request sets up GitHub code scanning for this repository. Once the scans have completed and the checks have passed, the analysis results for this pull request branch will appear on this overview. Once you merge this pull request, the 'Security' tab will show more code scanning analysis results (for example, for the default branch). Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results. For more information about GitHub code scanning, check out the documentation.

[kmk3]

This seems to be intended for when multiple languages are analysed in the same
workflow:

From https://docs.github.com/en/code-security/code-scanning/creating-an-advanced-setup-for-code-scanning/customizing-your-advanced-setup-for-code-scanning#configuring-a-category-for-the-analysis:

If you don't specify a category parameter in your workflow, GitHub will
generate a category name for you, based on the name of the workflow file
triggering the action, the action name, and any matrix variables. For
example:

• The .github/workflows/codeql-analysis.yml workflow and the analyze
  action will produce the category .github/workflows/codeql.yml:analyze.
• The .github/workflows/codeql-analysis.yml workflow, the analyze action,
  and the {language: javascript-typescript, os: linux} matrix variables
  will produce the category
  .github/workflows/codeql-analysis.yml:analyze/language:javascript-typescript/os:linux.

The category value will appear as the <run>.automationDetails.id property
in SARIF v2.1.0. For more information, see "SARIF support for code
scanning."

Not sure if adding this would actually help or only add noise, so closing.