fix requirements

requirements/base.in

@@ -28,3 +28,6 @@ fastjsonschema
 tweepy
 requests-cache
 wand
+httplib2<0.21.0,>=0.20.4
+icalendar==4.0.9
+pytz<2022.0,>=2021.3

requirements/base.txt

@@ -90,7 +90,7 @@ django-extensions==3.2.3
     # via -r base.in
 django-filter==22.1
     # via wagtail
-django-modelcluster==6.2.1
+django-modelcluster==6.0
     # via wagtail
 django-permissionedforms==0.1
     # via wagtail
@@ -124,6 +124,10 @@ html5lib==1.1
     # via
     #   wagtail
     #   weasyprint
+httplib2==0.20.4
+    # via -r base.in
+icalendar==4.0.9
+    # via -r base.in
 ics==0.7.2
     # via -r base.in
 idna==3.6
@@ -185,6 +189,8 @@ pygments==2.17.2
     # via ipython
 pyopenssl==24.0.0
     # via josepy
+pyparsing==3.1.1
+    # via httplib2
 pypdf2==3.0.1
     # via -r base.in
 pyphen==0.14.0
@@ -193,11 +199,14 @@ python-dateutil==2.8.2
     # via
     #   arrow
     #   celery
+    #   icalendar
     #   ics
-pytz==2024.1
+pytz==2021.3
     # via
+    #   -r base.in
     #   django-modelcluster
     #   djangorestframework
+    #   icalendar
     #   l18n
 pyyaml==6.0.1
     # via -r base.in