Bump pytz from 2020.1 to 2020.5

Bumps [pytz](https://github.com/stub42/pytz) from 2020.1 to 2020.5.
- [Release notes](https://github.com/stub42/pytz/releases)
- [Commits](https://github.com/stub42/pytz/compare/release_2020.1...release_2020.5)

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

requirements.txt

@@ -1,6 +1,6 @@
 asgiref==3.3.1
 Django==3.1.4
-pytz==2020.1
+pytz==2020.5
 sqlparse==0.4.1
 requests
 python-slugify