TT#42659 Delete unused variable after last commit

Last commit: 8142cd79a5

Change-Id: I77ee202548274dd7269f3f4536b19a38906d93e6

release_dashboard/utils/docker.py

@@ -80,8 +80,6 @@ def delete_docker_info(url):
         logger.debug("Debug mode, would trigger: %s", url)
     else:
         logger.debug("trigger: %s", url)
-        headers = {'accept':
-                   'application/vnd.docker.distribution.manifest.v2+json'}
         response = requests.delete(url)
         logger.debug("response: %s" % response)
         response.raise_for_status()