postfwd: Disable the email limits for gitlab

Since Gitlab causes high email traffic, apply the same rule as for the
aur by adding the sasl_username for gitlab to the no limits list.

Fix #564

roles/postfwd/templates/postfwd.cf.j2

@@ -11,6 +11,7 @@
 
 # no rate-limit for some authenticated users
 &&NO_RATE_LIMIT_USERS {
+        sasl_username=gitlab
         sasl_username=aur;
 };
 id=NoRateLimit;