Add $ to Demos (backport #5352)

[mergify]

---

This is an automatic backport of pull request #5352 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 8d1b99d has failed:

On branch mergify/bp/humble/pr-5352
Your branch is up to date with 'origin/humble'.

You are currently cherry-picking commit 8d1b99d.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   source/Tutorials/Demos/Content-Filtering-Subscription.rst
	modified:   source/Tutorials/Demos/Intra-Process-Communication.rst
	modified:   source/Tutorials/Demos/Rosbag-with-ROS1-Bridge.rst

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   source/Tutorials/Demos/Action-Introspection.rst
	both modified:   source/Tutorials/Demos/Logging-and-logger-configuration.rst
	both modified:   source/Tutorials/Demos/Quality-of-Service.rst
	both modified:   source/Tutorials/Demos/Real-Time-Programming.rst
	deleted by us:   source/Tutorials/Demos/Service-Introspection.rst
	both modified:   source/Tutorials/Demos/dummy-robot-demo.rst

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[github-actions]

HTML artifacts: https://github.com/ros2/ros2_documentation/actions/runs/14694283993/artifacts/3017622006.

To view the resulting site:

1. Click on the above link to download the artifacts archive
2. Extract it
3. Open html-artifacts-5392/index.html in your favorite browser