Updating dbi_dbccLastKnownGood I have a VLDB and I offload the DBCC CHECKDB to another server.  Is it possible to update the dbi_dbccLastKnownGood on the VLDB server so it passes any scripts that check that date like sp_Blitz?
No, this feature was put in to record the last time that DBCC CHECKDB ran successfully. It would be extremely unlikely that a feature would be added that allows this value to be edited at will and effectively lie about the history.

The only way to update this that does not actually involve hacking the database boot page is to execute DBCC CHECKDB.

So you should customise these scripts to not report that issue or ignore this result if it is entirely expected that this database isn't being checked due to alternate arrangements.