Fix missing bracket in config snippet

Add missing bracket in `connections` config snippet.


Co-authored-by: TaiwanChuChu <[email protected]>

Author: hms5232

docs/quick-start/configure-mongodb.txt

@@ -68,6 +68,7 @@ Configure Your MongoDB Connection
              'dsn' => env('DB_URI'),
              'database' => 'sample_mflix',
            ],
+         ],
 
          // ...