Bump numpy from 1.21.0 to 1.22.0 in /docs

Bumps [numpy](https://github.com/numpy/numpy) from 1.21.0 to 1.22.0.
- [Release notes](https://github.com/numpy/numpy/releases)
- [Changelog](https://github.com/numpy/numpy/blob/main/doc/HOWTO_RELEASE.rst)
- [Commits](numpy/numpy@v1.21.0...v1.22.0)

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

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

docs/requirements.txt

@@ -1,4 +1,4 @@
-numpy==1.21.0
+numpy==1.22.0
 tqdm==4.31.1
 ordered-set==3.1.1
 Sphinx==1.8.3