Drop base grenade job for nova

The grenade multinode job that nova runs is a superset of the base
grenade job. There is really no reason for us to run both, and doing
so consumes a lot of resources for no real gain.

Change-Id: If2608406776e0d5a06b726e65b55881e70562d18
diff --git a/zuul.d/integrated-gate.yaml b/zuul.d/integrated-gate.yaml
index 4c1ee5a..208f728 100644
--- a/zuul.d/integrated-gate.yaml
+++ b/zuul.d/integrated-gate.yaml
@@ -375,11 +375,9 @@
       run on Nova gate only.
     check:
       jobs:
-        - grenade
         - tempest-integrated-compute
     gate:
       jobs:
-        - grenade
         - tempest-integrated-compute
 
 - project-template: