Update ember to 6.0.1

Author: VasylMarchuk

app/components/course-page/course-stage-step/community-solution-card/content.hbs

@@ -17,7 +17,7 @@
         @highlightedFile={{highlightedFile}}
         @onPublishToGithubButtonClick={{this.handlePublishToGithubButtonClick}}
         @solution={{@solution}}
-        class={{if (not-eq index (sub @solution.highlightedFiles.length 1)) "mb-4"}}
+        class={{if (not-eq index (sub (or @solution.highlightedFiles.length 0) 1)) "mb-4"}}
       />
     {{/each}}
   {{else}}

config/ember-cli-update.json

@@ -3,7 +3,7 @@
   "packages": [
     {
       "name": "ember-cli",
-      "version": "5.12.0",
+      "version": "6.0.1",
       "blueprints": [
         {
           "name": "app",