Bump pytz from 2019.3 to 2020.1

Bumps [pytz](https://github.com/stub42/pytz) from 2019.3 to 2020.1.
- [Release notes](https://github.com/stub42/pytz/releases)
- [Commits](https://github.com/stub42/pytz/compare/release_2019.3...release_2020.1)

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -1,6 +1,6 @@
 asgiref==3.2.10
 Django==3.0.8
-pytz==2019.3
+pytz==2020.1
 sqlparse==0.3.1
 requests
 python-slugify