Bump pip from 20.1 to 20.1.1 in /.github/workflows

Bumps [pip](https://github.com/pypa/pip) from 20.1 to 20.1.1.
- [Release notes](https://github.com/pypa/pip/releases)
- [Changelog](https://github.com/pypa/pip/blob/master/NEWS.rst)
- [Commits](pypa/pip@20.1...20.1.1)

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

Author: dependabot[bot]

.github/workflows/constraints.txt

@@ -1,3 +1,3 @@
-pip==20.1
+pip==20.1.1
 nox==2019.11.9
 poetry==1.0.5