Bump pytz from 2021.1 to 2021.3

Bumps [pytz](https://github.com/stub42/pytz) from 2021.1 to 2021.3.
- [Release notes](https://github.com/stub42/pytz/releases)
- [Commits](stub42/pytz@release_2021.1...release_2021.3)

---
updated-dependencies:
- dependency-name: pytz
  dependency-type: indirect
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

docs-requirements.txt

@@ -28,7 +28,7 @@ pygments==2.10.0
     # via sphinx
 pyparsing==2.4.7
     # via packaging
-pytz==2021.1
+pytz==2021.3
     # via babel
 requests==2.26.0
     # via sphinx

test-requirements.txt

@@ -54,7 +54,7 @@ pytest==6.2.5
     #   pytest-cov
 pytest-cov==2.12.1
     # via -r test-requirements.in
-pytz==2021.1
+pytz==2021.3
     # via babel
 requests==2.26.0
     # via sphinx