pages/linux/*: generalize Fedora & Ubuntu version examples

[kbdharun]

• The page(s) are in the correct platform directories: common, linux, osx, windows, sunos, android, etc.
• The page description(s) have links to documentation or a homepage.
• The page(s) follow the content guidelines.
• The page(s) follow the style guide.
• The PR contains at most 5 new pages.
• The PR title conforms to the recommended templates.
• Version of the command being documented (if known):

[Managor]

Any way we could abstract these to not create continuous maintenance burden?

[kbdharun]

Any way we could abstract these to not create continuous maintenance burden?

Yeah, we could make the descriptions generic, but for placeholders I think it would be better to have specific examples.

[kbdharun]

I have updated the toolbox pages to have a generic wording, for tmt-try I have updated it to use the default rhel-9 example since it should be relevant for longer than Fedora due to its support cycle and for debootstrap I have updated it to use sid (Debian Unstable) which unlike other point releases won't have a different codename.