Enable merge barriers (#217)

Enable the `merge_barriers` setting in `.github/ops-bot.yaml` to enable the new merge barriers plugin.

Authors:
  - Kyle Edwards (https://github.com/KyleFromNVIDIA)

Approvers:
  - Bradley Dice (https://github.com/bdice)

URL: #217

Author: KyleFromNVIDIA

.github/ops-bot.yaml

@@ -7,3 +7,4 @@ label_checker: true
 release_drafter: true
 forward_merger: true
 recently_updated: true
+merge_barriers: true