Changes Emulation CI to weekly-periodic

Due to initial release of emulated architecture feature the CI
has been changed to run less frequent to save CI hours. This
will be revisited in later releases as feature gains greater
support and capabilities.

Implements: blueprint pick-guest-arch-based-on-host-arch-in-libvirt-driver
Signed-off-by: Jonathan Race <[email protected]>
Change-Id: I7b085c2086a720a049c9b04a6ff10a0e5cc9d650

Author: chateaulav

.zuul.yaml

@@ -649,7 +649,6 @@
         - nova-multi-cell
         - nova-next
         - nova-ovs-hybrid-plug
-        - nova-emulation
         - nova-tox-validate-backport:
             voting: false
         - nova-tox-functional-centos8-py36
@@ -721,6 +720,11 @@
             irrelevant-files: *nova-base-irrelevant-files
         - tempest-integrated-compute-centos-8-stream:
             irrelevant-files: *nova-base-irrelevant-files
+    periodic-weekly:
+      jobs:
+        # Runs emulation feature functionality test less frequently due
+        # to being the initial release and experimental in nature.
+        - nova-emulation
     experimental:
       jobs:
         - ironic-tempest-bfv: