remove tests for Ember 3.4 and 3.8

Author: mansona

.github/workflows/ci.yml

@@ -49,8 +49,6 @@ jobs:
     strategy:
       matrix:
         scenario:
-          - 'ember-lts-3.4'
-          - 'ember-lts-3.8'
           - 'ember-release'
           - 'ember-beta'
           - 'ember-canary'