Bugfix: Pages with handcrafted HTML tables throw JS errors related to sticky header library

What does this MR do and why?

This MR skips any non-standard tables and avoid adding sticky header to those. The sticky header table package requires that there is a header element, so when it's missing it will throw the following error:

Non-standard tables in our content do not have tag.

For example: https://new.docs.gitlab.com/administration/reference_architectures/#how-to-interpret-the-results

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Configure a local GitLab Docs environment: https://gitlab.com/gitlab-org/technical-writing/docs-gitlab-com/-/blob/main/doc/setup.md.
2. Run local environment and visit http://localhost:1313/administration/reference_architectures/#how-to-interpret-the-results, make sure there are no visual regressions and no JS errors.

Merge request acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this merge request.

Closes #179 (closed)