Downgrade log level from warning to info for "[warning] Could not find reference sequence for <gene> in the PRG so using the consensus path"

[leoisl]

Mabi got confused by this warning message, and I think the common use case for pandora is to actually not receive reference sequences for the genes and automatically infer it from the sample mappings. So I think this warning should be downgraded to info, as a warning seems to tell the user they did sth that might not be correct or unusual, which is not the case here.