Issue #3119921: Switch to use Claro as the default admin theme for Varbase

tests/features/varbase/step2-apply-tests/03-admin-management/03-00-pre-check-important-admin-development-pages.feature

@@ -87,7 +87,7 @@ So that I can use them after the install or update.
      Then I should see "Appearance"
       And I should see "Vartheme"
       And I should see "Vartheme (Bootstrap 4 - SASS)"
-      And I should see "Adminimal"
+      And I should see "Claro"
       And I should see "Bootstrap"
       And I should see "Bootstrap Barrio"
       And I should see "Vartheme Admin"

varbase.info.yml

@@ -21,10 +21,9 @@ install:
   - views
   - file
 themes:
-  - claro
-  - gin
   - bootstrap_barrio
   - vartheme_bs4
+  - claro
   - vartheme_admin
 
 interface translation project: varbase