Add missing type information to docs

Change-Id: Iac23d54512b23f031460d1b7281ccb8d93e20cad

plugins/modules/os_subnets_info.py

@@ -25,11 +25,13 @@ options:
         - Alias 'subnet' added in version 2.8.
      required: false
      aliases: ['subnet']
+     type: str
    filters:
      description:
         - A dictionary of meta data to use for further filtering.  Elements of
           this dictionary may be additional dictionaries.
      required: false
+     type: dict
 requirements:
     - "python >= 3.6"
     - "openstacksdk"