CI: Move to Ubuntu 2022.04 "Jammy" for CI base

- We now have a new enough sbsigntools in the distro, stop building.
- Use the 20220531 tag for Jammy.
- Move to pygit2 1.9.2 (current version) as the old one doesn't build on
 "Jammy".
- Add the working directory to the list of safe directories for git.

Signed-off-by: Tom Rini <trini@konsulko.com>