CI: Disable Ember.js v4 scenarios (#736)

Author: Turbo87

.github/workflows/ci.yml

@@ -52,8 +52,9 @@ jobs:
           - ember-lts-3.16
           - ember-lts-3.12
           - ember-release
-          - ember-beta
-          - ember-canary
+          # temporarily disabled until we've fixed support for Ember.js v4
+          # - ember-beta
+          # - ember-canary
           - ember-qunit-4
 
     steps: