Use a different flag for enabling the new Checks UI

The experimental flag has been broken up into one for Gerrit, one for
buildbucket and one for the old Checks plugin.

Change-Id: I324b34b5f7b1708ae800095f0e6c43fd45f94f61
diff --git a/gr-checks/gr-checks.js b/gr-checks/gr-checks.js
index e9e9c28..e439014 100644
--- a/gr-checks/gr-checks.js
+++ b/gr-checks/gr-checks.js
@@ -68,7 +68,7 @@
 
 Gerrit.install(plugin => {
   const experiments = window.ENABLED_EXPERIMENTS || [];
-  if (experiments.includes("UiFeature__ci_reboot_checks")) {
+  if (experiments.includes("UiFeature__ci_reboot_checks_checks")) {
     // Until end of 2020 this is only interesting for developing purposes. So
     // no real user is affected for the time being.
     console.log('Installing checks REBOOT plugin.');