fix: requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-PROTOBUF-10364902
- https://snyk.io/vuln/SNYK-PYTHON-URLLIB3-10390193
- https://snyk.io/vuln/SNYK-PYTHON-URLLIB3-10390194

Author: snyk-bot

requirements.txt

@@ -23,4 +23,6 @@ appdirs
 tqdm
 funcy
 fsspec
-opencv-python
+opencv-python
+protobuf>=4.25.8 # not directly required, pinned by Snyk to avoid a vulnerability
+urllib3>=2.5.0 # not directly required, pinned by Snyk to avoid a vulnerability