Do not allow triggers that run as part of REPLACE conflict resolution

during an UPDATE to modify the the table being updated.  Otherwise, those
triggers might delete content out from under the update operation, leading
to all kinds of problems.  Ticket [314cc133e5ada126]

FossilOrigin-Name: db4b7e1dc399c1f16b827ac087aa37c0815f4b2f41f1ffad59963eead2ab5562