Temporarily disable SQL Server Mirroring
From the documentation, you could just shutdown the witness instead of removing it from all the servers.
It says that the mirroring will then be a &quot;partner-to-partner&quot; quorum, and that no automatic failover will occur.
Of course, I would test it on a dev setup before trying it in production.

A partner-to-partner quorum that consists of the two partners.
As long as the partners retain quorum, the database continues in a SYNCHRONIZED state, and manual failover remains possible. Without the witness, automatic failover is not possible; but when the witness regains quorum, the session resumes regular operation, and automatic failover is supported again.