We use a new larger rsa key so that gitea checks on key size don't fail
when we upgrade gitea to 1.21 or newer. We did consider an ed25519 key
isntead but those keys can only be generated in the new openssh key file
format and there is some question around whether or not Gerrit's
replication plugin (ultimately MINA ssh client) can read those files. To
be safe we stick with what we know works and simply increase the bit
count.
Change-Id: I51e97e8545a54202b05f32de70c0715083954119
91322002ff