Update ubuntu-slim reference to include link

[maflcko]

Just like Ubuntu 22.04 includes a link to the readme, the ubuntu-slim one should contain a link as well, for consistency, and accessibility.

For reference, the link on the main branch for Ubuntu 22.04:

docs/data/reusables/actions/supported-github-runners.md

Line 27 in 28dc5b5

<code><a href="https://github.com/actions/runner-images/blob/main/images/ubuntu/Ubuntu2204-Readme.md">ubuntu-22.04</a></code>

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