Bump numpy from 1.19.3 to 1.19.4 (#1909)

Bumps [numpy](https://github.com/numpy/numpy) from 1.19.3 to 1.19.4.
- [Release notes](https://github.com/numpy/numpy/releases)
- [Changelog](https://github.com/numpy/numpy/blob/master/doc/HOWTO_RELEASE.rst.txt)
- [Commits](https://github.com/numpy/numpy/compare/v1.19.3...v1.19.4)

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

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

requirements.txt

@@ -8,7 +8,7 @@ matplotlib==3.3.2
 mercurial==5.5.2
 microannotate==0.0.20
 mozci==1.9.4
-numpy==1.19.3
+numpy==1.19.4
 orjson==3.4.3
 ortools==8.0.8283
 pandas==1.1.4