Bump numpy from 1.19.3 to 1.19.4

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](numpy/numpy@v1.19.3...v1.19.4)

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

requirements.txt

@@ -1,6 +1,6 @@
 # Setup requirements
 cython==0.29.21
-numpy==1.19.3
+numpy==1.19.4
 
 # Drakkar-Software requirements
 async-channel>=2.0.3, <2.1