Use Wagtail 2.13 for bakery demo and GitPod.

requirements/base.txt

@@ -1,4 +1,4 @@
 Django>=3.1,<3.2
 django-dotenv==1.4.1
-wagtail>=2.12,<2.13
+wagtail>2.12,<=2.13
 wagtailfontawesome>=1.1.3,<1.2