fix: requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-NUMPY-2321964
- https://snyk.io/vuln/SNYK-PYTHON-NUMPY-2321966
- https://snyk.io/vuln/SNYK-PYTHON-NUMPY-2321969
- https://snyk.io/vuln/SNYK-PYTHON-NUMPY-2321970
- https://snyk.io/vuln/SNYK-PYTHON-NUMPY-73513

Author: snyk-bot

requirements.txt

@@ -4,6 +4,6 @@ tensorflow==1.15.4
 dlib==19.16.0
 opencv_python==3.4.3.18
 imutils==0.5.1
-numpy==1.15.2
+numpy==1.22.2
 matplotlib==3.0.0
 scipy==1.1.0