Prevent unknown params passed to tempest charm

See: https://bugs.launchpad.net/juju/+bug/2051187

By default, juju allows extra params to be passed to an action.
This is risky here, because if a user makes a typo on a parameter,
it could be the difference between running a small fast set of tests,
or a very large slow set of tests...
For example, if the test-list or regex params are typoed.

Change-Id: Ic6daaab66b6187e8fb6151d861a0ba82e72ed756

charms/tempest-k8s/charmcraft.yaml

@@ -106,6 +106,7 @@ actions:
       - found in test list "list1"
       - AND match regex "one" or "two"
       - AND don't match regex "three"
+    additionalProperties: false
     params:
       regex:
         type: string
@@ -136,3 +137,4 @@ actions:
 
   get-lists:
     description: List existing test lists, to be used with validate action.
+    additionalProperties: false