Add link to Tracy Linux AppImage once a new stable release of Tracy is made

**Your Godot version:** 4.7

**Issue description:** There used to be no official pre-built binary of the Tracy server for Linux, but [this has changed recently](https://github.com/wolfpld/tracy/issues/893#issuecomment-5219390844). No stable release is available yet, but it can already be [downloaded on GitHub Actions](https://github.com/wolfpld/tracy/actions/workflows/appimage.yml). Once a stable release is made, we should change the documentation accordingly.

**URL to the documentation page (if already existing):** https://docs.godotengine.org/en/latest/engine_details/development/profiling/tracy.html#get-the-tracy-server

Open the linked Tracy documentation page and locate the “Get the Tracy server” section. After Tracy publishes a stable release, update that section to link to the Linux AppImage, then verify the documentation renders correctly and the stable-release download is reachable.

Written by the indexing model from the issue text.