revise actions descriptions for accuracy and spelling

actions.yaml

@@ -1,14 +1,14 @@
 replace-munge-key:
   description: >
-    Replace the existing munge key with the munge key from the secrets store.
+    Replace the existing munge-key with the munge-key from the secrets store.
     Example usage:
     $ juju run-action munge/0 replace-munge-key
 rotate-munge-key:
   description: >
     Rotate the munge-key. Replace the munge-key with the key specified as input to
     this action. If no value is specified than a new munge-key will be generated by the charm.
     Example usage:
-    $ juju run-action munge/leader rotate-munge-key munge-key="$(cat munge.key | base64)"
+    $ juju run munge/0 rotate-munge-key munge-key="$(cat munge.key | base64)"
   params:
     munge-key:
       type: string