added label_checker: true to ops-bot.yaml (#713)

Author: rockhowse

.github/ops-bot.yaml

@@ -0,0 +1,9 @@
+# This file controls which features from the `ops-bot` repository below are enabled.
+# - https://github.com/rapidsai/ops-bot
+
+auto_merger: false
+branch_checker: false
+label_checker: true
+release_drafter: false
+recently_updated: false
+forward_merger: false