Revert "[REF] Code readability changes on activity tokens."

Per https://docs.civicrm.org/dev/en/latest/framework/token/#token-processor
The contactId is actually documented. While I've been removing those in various places in
favour of contactID or contact_id it seems Tim has been putting them in so
I think it's safer to revert this change at this stage

This reverts commit 2ebb452b.