Bump pip from 21.1 to 23.3

Bumps [pip](https://github.com/pypa/pip) from 21.1 to 23.3.
- [Changelog](https://github.com/pypa/pip/blob/main/NEWS.rst)
- [Commits](pypa/pip@21.1...23.3)

---
updated-dependencies:
- dependency-name: pip
  dependency-type: direct:production
...

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

requirements.txt

@@ -3,4 +3,4 @@
 setuptools==44.1.1
 zc.buildout==3.0.0rc1
 wheel==0.37.1
-pip==21.1
+pip==23.3