Upgrade to JGit 3.3.2

Includes a bug fix to only reset credentials after multiple attempts.

See https://git.eclipse.org/c/jgit/jgit.git/commit/?h=stable-3.3&id=a53a18e988714cd87934d1a7e29b3331b37542a8

No automated tests currently evaluate authenticated access, so it is
not clear if that bug fix is relevant or not.