WSL2 fixes

[hamishwillee]

Fixes to WSL2 docs, in particular removing no-longer-valid restrictions on Windows 10 and explaining how to work with multiple versions of Ubuntu.

FYI @MaEtUgR

[github-actions]

No flaws found

[MaEtUgR]

Thanks @hamishwillee for the improvements! They were put to use when I just installed on a new machine 👍
Is the kisak-mesa part to get gz running out of the box? I still have to try this. My non-automated way so far was along the lines of PX4/PX4-Autopilot#21712

[hamishwillee]

@MaEtUgR The kisak-mesa isn't "required" to get things running out of the box, which is why I put it in troubleshooting. Until I installed those latest drivers I was getting segfaults on closing the simulation. I'd rather not recommend this by default because at some point the default drivers should be good enough. But if you feel differently I will take direction from you!

There was a very long discussion that lead to all of this in gazebosim/gz-sim#920