Rename job_summary_dict to job_metadata

* Clarifies purpose of notification template variable

awx/main/tests/functional/models/test_notifications.py

@@ -87,7 +87,7 @@ class TestJobNotificationMixin(object):
                                  'use_fact_cache': bool,
                                  'verbosity': int},
                          'job_friendly_name': str,
-                         'job_summary_dict': str,
+                         'job_metadata': str,
                          'url': str}