system-config-run-gitea: use standard bridge host

In what looks like a typo, we are overriding the bridge node for this
test to a bionic host.  Remove this.  This was detected by testing an
upgraded Ansible, which wouldn't install on the lower python on
Bionic.

Change-Id: Ie3e754598c6da1812e74afa914f50d91972012cd

zuul.d/system-config-run.yaml

@@ -616,7 +616,6 @@
     nodeset:
       nodes:
         - <<: *bridge_node_x86
-          label: ubuntu-bionic
         - name: gitea-lb02.opendev.org
           label: ubuntu-jammy
         - name: gitea99.opendev.org