Update sample config

docs/sample_config.yaml

@@ -518,6 +518,9 @@ log_config: "CONFDIR/SERVERNAME.log.config"
 #   - one for login that ratelimits login requests based on the account the
 #     client is attempting to log into, based on the amount of failed login
 #     attempts for this account.
+#   - one for ratelimiting redactions by room admins. If this is not explicitly
+#     set then it uses the same ratelimiting as per rc_message. This is useful
+#     to allow room admins to quickly deal with abuse quickly.
 #
 # The defaults are as shown below.
 #
@@ -539,6 +542,10 @@ log_config: "CONFDIR/SERVERNAME.log.config"
 #  failed_attempts:
 #    per_second: 0.17
 #    burst_count: 3
+#
+#rc_admin_redaction:
+#  per_second: 1
+#  burst_count: 50
 
 
 # Ratelimiting settings for incoming federation