Fix Zuul warnings with regexps

zuul now reports warnings when using perl-style regexp:
| The RE2 syntax error is: invalid perl operator: (?!

for
| branches: ^(?!stable)

This commit fixes it by using the correct RE2 syntax

Change-Id: Id647cc71ec6fc982a152960e112fe5c63da01767

zuul.d/jobs.yaml

@@ -164,7 +164,9 @@
     description: |
       Run tox python 3.9 functional against master of sqlalchemy and related projects
     # The job only tests the latest and shouldn't be run on the stable branches
-    branches: ^(?!stable)
+    branches:
+       regex: ^stable
+       negate: true
     required-projects:
       - name: openstack/oslo.db
       - name: github.com/sqlalchemy/sqlalchemy

zuul.d/projects.yaml

@@ -122,9 +122,13 @@
     periodic:
       jobs:
         - publish-openstack-octavia-amphora-image-focal:
-            branches: ^(?!stable/.*).*$
+            branches:
+              regex: ^stable/.*$
+              negate: true
         - publish-openstack-octavia-amphora-image-centos-9-stream:
-            branches: ^(?!stable/.*).*$
+            branches:
+              regex: ^stable/.*$
+              negate: true
         - octavia-amphora-image-build
 # Putting octavia-v2-dsvm-scenario-fips in periodic as centos 8 is too slow
         - octavia-v2-dsvm-scenario-fips: