Bump numpy from 1.14.5 to 1.22.0 in /xfer-ml/docs (#87)

Bumps [numpy](https://github.com/numpy/numpy) from 1.14.5 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@v1.14.5...v1.22.0)

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

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

xfer-ml/docs/requirements.txt

@@ -1,4 +1,4 @@
 Sphinx==1.7.7
 nbsphinx==0.3.4
 sphinx-rtd-theme==0.4.1
-numpy==1.14.5
+numpy==1.22.0