Bump attrs from 20.3.0 to 21.2.0

Bumps [attrs](https://github.com/python-attrs/attrs) from 20.3.0 to 21.2.0.
- [Release notes](https://github.com/python-attrs/attrs/releases)
- [Changelog](https://github.com/python-attrs/attrs/blob/main/CHANGELOG.rst)
- [Commits](python-attrs/attrs@20.3.0...21.2.0)

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

requirements.txt

@@ -1,5 +1,5 @@
 algoliasearch==2.4.0
-attrs==20.3.0
+attrs==21.2.0
 bcrypt==3.2.0
 certifi==2020.12.5
 cffi==1.14.5