Bump pip from 21.2.4 to 21.3.1

Bumps [pip](https://github.com/pypa/pip) from 21.2.4 to 21.3.1.
- [Release notes](https://github.com/pypa/pip/releases)
- [Changelog](https://github.com/pypa/pip/blob/main/NEWS.rst)
- [Commits](pypa/pip@21.2.4...21.3.1)

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

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

requirements.txt

@@ -13,7 +13,7 @@ grpcio==1.42.0
 grpcio-status==1.42.0
 idna==3.3
 packaging==21.3
-pip==21.2.4
+pip==21.3.1
 proto-plus==1.19.8
 protobuf==3.19.1
 pyasn1==0.4.8