Move infra-specs and infra-manual to v3 only

To be able to test specs and docs post jobs, move these two repos to
Zuul v3. Disable all Zuul v2 testing.

Change-Id: I5646ab81eb1a6515b32c42a2c3c4e64a94be4748

zuul.d/projects.yaml

@@ -770,13 +770,13 @@
     name: openstack-infra/infra-manual
     templates:
       - merge-check
-    check:
+    infra-check:
       jobs:
         - build-openstack-sphinx-docs
-    gate:
+    infra-gate:
       jobs:
         - build-openstack-sphinx-docs
-    post:
+    infra-post:
       jobs:
         - publish-infra-manual
 
@@ -784,7 +784,19 @@
     name: openstack-infra/infra-specs
     templates:
       - merge-check
-      - openstack-specs-jobs
+      # TODO(jaegerandi): use the openstack-specs-jobs once we moved 
+      # to zuul v3 everywhere:
+      # - openstack-specs-jobs
+    infra-check:
+      jobs:
+        - build-openstack-sphinx-docs
+    infra-gate:
+      jobs:
+        - build-openstack-sphinx-docs
+    infra-post:
+      jobs:
+        - publish-openstack-specs
+
 
 - project:
     name: openstack-infra/irc-meetings

zuul/layout.yaml

@@ -4011,16 +4011,6 @@ projects:
     gate:
       - gate-infra-ansible
 
-  - name: openstack-infra/infra-manual
-    template:
-      - name: merge-check
-      - name: infra-publish-jobs
-
-  - name: openstack-infra/infra-specs
-    template:
-      - name: merge-check
-      - name: openstack-specs-jobs
-
   - name: openstack-infra/irc-meetings
     template:
       - name: merge-check