Remove unused 'hideProjects' prop and its related refs

What does this MR do and why?

Fixes #385664 (closed)

Remove unused 'hideProjects' prop and its related refs

Changelog: other

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

app/assets/javascripts/groups/components/app.vue

@@ -41,10 +41,6 @@ export default {
       type: Object,
       required: true,
     },
-    hideProjects: {
-      type: Boolean,
-      required: true,
-    },
   },
   data() {
     return {