Update cephadm collection version

Author: bbezak

etc/kayobe/ansible/requirements.yml

@@ -1,7 +1,7 @@
 ---
 collections:
   - name: stackhpc.cephadm
-    version: 1.14.0
+    version: 1.15.1
   # NOTE: Pinning pulp.squeezer to 0.0.13 because 0.0.14+ depends on the
   # pulp_glue Python library being installed.
   - name: pulp.squeezer