[CI] Remove periodic jobs from unmaintained branch

There is no need to run periodics in unmaintained branches, they just
consume resource and teams are not checking the results.

Change-Id: Ib76946863e1205f2500d76e4172eea8b1985c271

zuul.d/projects.yaml

@@ -3,7 +3,6 @@
 - project:
     templates:
       - check-requirements
-      - periodic-stable-jobs-neutron
       - openstack-cover-jobs
       - openstack-python3-zed-jobs
       - publish-openstack-docs-pti
@@ -114,13 +113,6 @@
         - octavia-v2-dsvm-scenario
         - octavia-v2-dsvm-tls-barbican
         - octavia-grenade
-    periodic:
-      jobs:
-        - octavia-amphora-image-build
-        - octavia-grenade-ffu
-# Putting octavia-v2-dsvm-scenario-fips in periodic as centos 8 is too slow
-        - octavia-v2-dsvm-scenario-fips:
-            voting: false
     experimental:
       jobs:
         - octavia-v2-dsvm-scenario-nftables