Bump pip-tools from 5.5.0 to 6.0.1

Bumps [pip-tools](https://github.com/jazzband/pip-tools) from 5.5.0 to 6.0.1.
- [Release notes](https://github.com/jazzband/pip-tools/releases)
- [Changelog](https://github.com/jazzband/pip-tools/blob/master/CHANGELOG.md)
- [Commits](jazzband/pip-tools@5.5.0...6.0.1)

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

requirements.txt

@@ -3,7 +3,7 @@ bleach==3.3.0
 bleach-allowlist==1.0.3
 gdata==2.0.18
 isodate==0.6.0
-pip-tools==5.5.0
+pip-tools==6.0.1
 Markdown==3.3.4
 pytz==2021.1
 smartypants==2.0.1