Issue #3480746 by pfrenssen: Update Gitlab CI template now that Drupal 11 is the default version

.gitlab-ci.yml

@@ -21,12 +21,10 @@ include:
 ################
 # Pipeline configuration variables are defined with default values and descriptions in the file
 # https://git.drupalcode.org/project/gitlab_templates/-/blob/main/includes/include.drupalci.variables.yml
-# Uncomment the lines below if you want to override any of the variables. The following is just an example.
 ################
-# variables:
-#   SKIP_ESLINT: '1'
-#   OPT_IN_TEST_NEXT_MAJOR: '1'
-#   _CURL_TEMPLATES_REF: 'main'
+variables:
+  # Keep testing on Drupal 10 until our dependencies are D11 ready.
+  CORE_STABLE: $CORE_PREVIOUS_STABLE
 
 phpcs:
   allow_failure: false