Adopt openstack/openstack as TC repository

openstack/openstack is a technical repository that contains
references for other changes in openstack official repositories.

To avoid an unnecessary rename, we should adopt it as a TC repo.

Change-Id: I1abbbd71bfde755d6cd4e4fdaccb8a1d44afbfaa

reference/technical-committee-repos.yaml

@@ -1,6 +1,7 @@
 ---
 # List of repositories owned by the technical committee
 Technical Committee:
+  - repo: openstack/openstack
   - repo: openstack/governance
   - repo: openstack/openstack-specs
   - repo: openstack/project-navigator-data