ci: Update FIPS test job to Go 1.20
Back when we migrated to Go 1.20 we didn't yet have a FIPS-enabled image for that Go version available. Now we do, so let's update our CI job to use the new Go version.
Back when we migrated to Go 1.20 we didn't yet have a FIPS-enabled image for that Go version available. Now we do, so let's update our CI job to use the new Go version.