[chore] Remove no longer needed front matter properties

[thompson-tomo]

Changes

Removed path_base_for_github_subdir from Hugo front matter example in contributing as we stopped using it with #1846

Important

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PRs that do not follow the guidance above, may be automatically rejected and closed.

Merge requirement checklist

• CONTRIBUTING.md guidelines followed.
• Change log entry added, according to the guidelines in When to add a changelog entry.
  • If your PR does not need a change log, start the PR title with [chore]
• Links to the prototypes or existing instrumentations (when adding or changing conventions)