Revert "Disable GLOBAL_VENV in grenade"

This reverts commit 4b787aaba5.

Reason for revert:
The fix to support GLOBAL_VEN was backported to the source version.

Change-Id: I29b13b85c3f512d9be98fb21794cf30dbf8eddde
Depends-on: https://review.opendev.org/c/openstack/designate/+/932905

.zuul.yaml

@@ -151,11 +151,6 @@
         c-bak: false
       grenade_localrc:
         BASE_RUN_SMOKE: False
-      # TODO(tkajinam): We should remove this once we fix failing manage.py
-      #                 command
-      grenade_devstack_localrc:
-        shared:
-          GLOBAL_VENV: false
       tox_envlist: all
       tempest_plugins:
         - designate-tempest-plugin