Remove outadted secret mirroring config

Author: alvaroaleman

core-services/prow/02_config/_plugins.yaml

@@ -2952,16 +2952,6 @@ config_updater:
         vsphere:
         - ocp
       name: base-repos
-    core-services/secret-mirroring/_mapping.yaml:
-      clusters:
-        app.ci:
-        - ci
-        build01:
-        - ci
-        build02:
-        - ci
-      key: mapping.yaml
-      name: secret-mirroring
 external_plugins:
   3scale/3scale-operator:
   - endpoint: http://refresh