Add pytz to requirements-testing.txt

Author: cclauss

requirements/requirements-testing.txt

@@ -2,6 +2,7 @@
 pytest>=7.0.1,<8.0
 pytest-cov>=4.0.0,<5.0
 pytest-django>=4.5.2,<5.0
+pytz
 importlib-metadata<5.0
 # temporary pin of attrs
 attrs==22.1.0