Release PBR 5.11.1

This addresses some testing-related issues with tox v4, but more
importantly also fixes a latent concurrency bug which tox v4 exposes
in PBR-using projects.

Change-Id: Ia5ac5672c294e3689b35cd569827e3f8f6a03b5e

deliverables/_independent/pbr.yaml

@@ -233,5 +233,9 @@ releases:
     projects:
       - repo: openstack/pbr
         hash: 45d4c9f02fafb425e61a18bbd7a20ef456293a56
+  - version: 5.11.1
+    projects:
+      - repo: openstack/pbr
+        hash: 98c84b5f87b89573ea6930bc783f07f2dd5ae8fd
 repository-settings:
   openstack/pbr: {}