Bump pip-tools from 5.2.0 to 5.2.1

Bumps [pip-tools](https://github.com/jazzband/pip-tools) from 5.2.0 to 5.2.1.
- [Release notes](https://github.com/jazzband/pip-tools/releases)
- [Changelog](https://github.com/jazzband/pip-tools/blob/master/CHANGELOG.md)
- [Commits](jazzband/pip-tools@5.2.0...5.2.1)

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

requirements.txt

@@ -25,7 +25,7 @@ mccabe==0.6.1             # via flake8
 more-itertools==4.1.0     # via pytest
 natsort==7.0.1            # via croniter
 packaging==20.3           # via pytest, sphinx
-pip-tools==5.2.0          # via -r requirements.in
+pip-tools==5.2.1          # via -r requirements.in
 pluggy==0.13.1            # via pytest
 py==1.5.3                 # via pytest
 pycodestyle==2.6.0        # via flake8