Switch to Ubuntu 22.04

[timja]

No description provided.

[basil]

This upgraded Git from 2.17.1 to 2.34.1, which broke https://github.com/jenkins-infra/release/blob/927a48721960a027dafbbee8950add22a3a2a84a/utils/release.bash#L414= because Git 2.27 adds a new warning:

+ git pull
From github.com:jenkinsci/jenkins
   a4f9f5b64b..b650de6960  master     -> origin/master
hint: You have divergent branches and need to specify how to reconcile them.
hint: You can do so by running one of the following commands sometime before
hint: your next pull:
hint: 
hint:   git config pull.rebase false  # merge (the default strategy)
hint:   git config pull.rebase true   # rebase
hint:   git config pull.ff only       # fast-forward only
hint: 
hint: You can replace "git config" with "git config --global" to set a default
hint: preference for all repositories. You can also pass --rebase, --no-rebase,
hint: or --ff-only on the command line to override the configured default per
hint: invocation.
fatal: Need to specify how to reconcile divergent branches.
script returned exit code 128

To fix this git pull should be updated to e.g. git pull --rebase.

[timja]

I did one option here which restored the same value as before:
#39

happy to switch it to rebase if you think it's a better option

[basil]

I have a slight subjective preference for rebase because the merge commits interfere with my OCD, but it really does not matter one way or another.