Bump numpy from 1.21.3 to 1.21.4

Bumps [numpy](https://github.com/numpy/numpy) from 1.21.3 to 1.21.4.
- [Release notes](https://github.com/numpy/numpy/releases)
- [Changelog](https://github.com/numpy/numpy/blob/main/doc/HOWTO_RELEASE.rst.txt)
- [Commits](https://github.com/numpy/numpy/compare/v1.21.3...v1.21.4)

---
updated-dependencies:
- dependency-name: numpy
dependency-type: direct:production
update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

requirements.txt

@@ -1,7 +1,7 @@
 aiortc==1.2.1
 av==8.0.3
 matplotlib==3.4.3
-numpy==1.21.3
+numpy==1.21.4
 opencv-python-headless==4.5.4.60
 pydub==0.25.1
 streamlit==1.2.0