build(deps): bump pip from 21.0 to 21.1.3 in /.github/workflows

Bumps [pip](https://github.com/pypa/pip) from 21.0 to 21.1.3.
- [Release notes](https://github.com/pypa/pip/releases)
- [Changelog](https://github.com/pypa/pip/blob/main/NEWS.rst)
- [Commits](pypa/pip@21.0...21.1.3)

---
updated-dependencies:
- dependency-name: pip
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

.github/workflows/constraints.txt

@@ -1,4 +1,4 @@
-pip==21.0
+pip==21.1.3
 pre-commit==2.9.3
 black==20.8b1
 flake8==3.9.2