Revert file name changes to fix menu and links for macOS installation

[azeey]

🦟 Bug fix

Summary

In #414 the file names install_osx.md and install_osx_src.md were changed, which broke links and side menu as shown in the picture below. Notice the missing menu item for macOS installation.

This reverts the file name change while keeping the rest of the changes in the PR. We can eventually rename the files as well, but that would require creating redirects so we don't break existing references on the internet.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.