fix: requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-PROTOBUF-15090738

Author: snyk-bot

requirements.txt

@@ -17,7 +17,7 @@ oauthlib==3.1.0
 opencv-contrib-python>=4.2.0.34
 opencv-python>=4.2.0.34
 Pillow
-protobuf==3.15.1
+protobuf==6.33.5
 pyasn1==0.4.8
 pyasn1-modules==0.2.8
 pytesseract==0.3.7