Switch to new grenade job name

The integrated gate templates has switched to the new grenade name
(grenade-py3 -> grenade). This repo uses an integrated gate template
but also listed the job 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

Change-Id: I0a981738034468bc8e0ef2944cb8b2b7a68e3851

.zuul.yaml

@@ -3,7 +3,7 @@
 - project:
     templates:
       # The integrated-gate-placement template adds the
-      # tempest-integrated-placement and grenade-py3 jobs.
+      # tempest-integrated-placement and grenade jobs.
       # tempest-integrated-placement runs a subset of tempest tests which are
       # relevant for placement, e.g. it does not run keystone tests.
       - check-requirements
@@ -40,7 +40,7 @@
               - ^releasenotes/.*$
               - ^tools/.*$
               - ^tox.ini$
-        - grenade-py3:
+        - grenade:
             irrelevant-files: *gate-irrelevant-files
         - tempest-ipv6-only:
             irrelevant-files: *gate-irrelevant-files
@@ -52,7 +52,7 @@
         - placement-nova-tox-functional-py37
         - tempest-integrated-placement:
             irrelevant-files: *gate-irrelevant-files
-        - grenade-py3:
+        - grenade:
             irrelevant-files: *gate-irrelevant-files
         - tempest-ipv6-only:
             irrelevant-files: *gate-irrelevant-files