Shelf permissions: Removed unused 'create' permission from view

Was causing confusion.
Added test to cover.
Also added migration to remove existing create entries to pre-emptively
avoid issues in future if 'create' is used again.

database/migrations/2023_06_25_181952_remove_bookshelf_create_entity_permissions.php

@@ -0,0 +1,29 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Support\Facades\DB;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        DB::table('entity_permissions')
+            ->where('entity_type', '=', 'bookshelf')
+            ->update(['create' => 0]);
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        // No structural changes to make, and we cannot know the permissions to re-assign.
+    }
+};