Fix Ubuntu support timeline and formatting

[Gold856]

This puts back the original wording that I had and shifts all the versions up by one LTS.

[PeterJohnson]

This may need a table formatting fix as well? The current one doesn't render as a table at https://docs.wpilib.org/en/2027/docs/software/what-is-wpilib.html

[sciencewhiz]

Unfortunately, we still use rst table formatting, instead of md table formatting. https://docutils.sourceforge.io/docs/ref/rst/restructuredtext.html#grid-tables