Switch to new grenade job name
Switch to new grenade job name

The integrated gate template (integrated-gate-py3) has been switched
to the new grenade name (grenade-py3 -> grenade). This repo uses the
template but also has for irrelevant files an extra entry.

Rename the job following the template change to avoid duplicate
grenade runs.

Details:
- http://lists.openstack.org/pipermail/openstack-discuss/2020-May/014602.html

Depends-On: https://review.opendev.org/725148
Change-Id: I73e67c0e01ca231678903b2460dab672f17251e3

openstack-dev/devstack,nawawi/openstack,nawawi/openstack,openstack-dev/devstack