Remove unused non-standard tags and nodes support

[tfoote]

Focused on freeing up page space and reducing indexing complexity.

[github-actions]

Site Test Render: https://github.com/ros-infrastructure/rosindex/actions/runs/17589187026/artifacts/3966764628.

To view the resulting site:

1. Click on the above link to download the artifacts archive
2. Extract it
3. View it using your favorite local rendering tool.
   a. As one example: Run ghrocker --devel rosindex-test-render-595 Requires ghrocker installed https://github.com/tfoote/ghrocker
   b. Open http://localhost:4000 in your favorite browser

[tfoote]

For reference it's removing the "No category tags"

And "Additional Links" conditionally:

[kscottz]

I don't see anything that is going to explode. Give it a shot.