Google stopped using information from emails as part of ad selection years ago, the ads shown in Gmail are based entirely on the other ad personalization data they have from other Google properties. They obviously still parse email contents for spam blocking and such, but that seems like a necessary part of running any webmail service, and not a profit center for them.

I guess it's always possible that they're lying about it, but given the depth of the regulatory and public relations fiasco that would cause I'd be very surprised.