Fix typo in flowstate configuration (#306)

See https://sentry.io/organizations/mozilla/issues/3717438384/?project=6364263

Author: leplatrem

config/config.prod.yaml

@@ -61,7 +61,7 @@
         - maybe_update_issue_resolution
         - maybe_update_issue_status
       existing:
-        - update_issue,
+        - update_issue
         - maybe_assign_jira_user
         - maybe_update_issue_resolution
         - maybe_update_issue_status