Bump numpy from 1.15.4 to 1.22.0

Bumps [numpy](https://github.com/numpy/numpy) from 1.15.4 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@v1.15.4...v1.22.0)

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

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

Author: dependabot[bot]

requirements.txt

@@ -2,7 +2,7 @@ certifi==2018.10.15
 chardet==3.0.4
 idna==2.7
 nltk==3.3
-numpy==1.15.4
+numpy==1.22.0
 oauthlib==2.1.0
 pandas==0.23.4
 PySocks==1.6.8