test(docs-infra): run a11y tests against /tutorial and update a11y scores (#41103)

This commit adds `/tutorial` to the list of angular.io pages that we run
a11y tests against and updates the required scores to match the current
ones (to avoid a future regression going unnoticed).

PR Close #41103

aio/scripts/test-aio-a11y.js

@@ -26,8 +26,9 @@ const MIN_SCORES_PER_PAGE = {
   'cli': 98,
   'cli/add': 98,
   'docs': 100,
-  'guide/docs-style-guide': 95,
+  'guide/docs-style-guide': 96,
   'start': 98,
+  'tutorial': 98,
 };
 
 // Run