Remove Django modelcluster submodule

.gitmodules

@@ -4,6 +4,3 @@
 [submodule "wagtail-localize"]
 	path = wagtail-localize
 	url = https://github.com/wagtail/wagtail-localize.git
-[submodule "django-modelcluster"]
-	path = django-modelcluster
-	url = https://github.com/wagtail/django-modelcluster.git

django-modelcluster

@@ -1 +0,0 @@
-Subproject commit c1a2729bc6b5eb24cdf7eb740e366454f923e2a1

requirements/base.txt

@@ -1,6 +1,5 @@
 Django>=3.1,<3.2
 django-dotenv==1.4.1
--e ./django-modelcluster
 -e ./wagtail[testing]
 -e ./wagtail-localize[testing,google_translate,git]
 wagtailfontawesome>=1.1.3,<1.2