Raise stable pulp job timeout to 12h

The stable pulp deb-upload jobs republish their entire Pulp repo on every package upload. These repos have accumulated hundreds of versions with nothing pruning them, so publishes have grown slow enough to exceed the default 4h job timeout, forcing repeated manual retries during releases (most recently the 19.1/19.2/19.3 patch cycle).

Temporary measure until the underlying Pulp slowness is fixed - tracked in gitlab-com/gl-infra/production-engineering#29705.

Will be backported to 19-1-stable, 19-2-stable, and 19-3-stable to unblock the current stuck patch pipelines.