Require SUnit as amber/core/SUnit.

amber_core is only an alias, kept by a map entry. The Node test runner
loads through amdefine, which has no map, so test_runner.js stopped with
"Cannot find module 'amber_core/SUnit'". contrib-legacy moved to
amber/core in its deps long ago.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

deploy.js

@@ -4,7 +4,7 @@ define([
     "amber/web/Web",
     "silk/Silk",
     "silk/Silk-Tests",
-    "amber_core/SUnit",
+    "amber/core/SUnit",
     'amber/legacy/IDE',
     'profstef/ProfStef'
     // --- packages to be deployed end here ---

testing.js

@@ -1,6 +1,6 @@
 define([
     './deploy',
-    'amber_core/SUnit',
+    'amber/core/SUnit',
     // --- packages used only during automated testing begin here ---
     // --- packages used only during automated testing end here ---
 ], function (amber) {