Secret is not permitted for public clients

OpenConext/OpenConext-manage#495

Author: oharsta

roles/manage/templates/metadata_configuration/oidc10_rp.schema.json.j2

@@ -698,7 +698,6 @@
       "required": [
         "name:en",
         "OrganizationName:en",
-        "secret",
         "grants"
       ],
       "additionalProperties": false