jira: Specify the correct argument type (#3368)

By default, all arguments are considered strings, but the module code expects the `fields` parameter to be a proper Python dictionary.

Fixes #2600

lib/ansible/modules/extras/web_infrastructure/jira.py

@@ -311,7 +311,7 @@ def main():
             comment=dict(),
             status=dict(),
             assignee=dict(),
-            fields=dict(default={})
+            fields=dict(default={}, type='dict')
         ),
         supports_check_mode=False
     )