fix: requirements/base.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-CERTIFI-3164749
- https://snyk.io/vuln/SNYK-PYTHON-CERTIFI-5805047
- https://snyk.io/vuln/SNYK-PYTHON-PYJWT-2840625
- https://snyk.io/vuln/SNYK-PYTHON-REQUESTS-5595532

requirements/base.txt

@@ -28,3 +28,6 @@ tqdm==4.64.1  # https://github.com/tqdm/tqdm
 selenium==4.7.0  # https://github.com/SeleniumHQ/selenium
 matplotlib==3.6.2  # https://github.com/matplotlib/matplotlib
 vk-api==11.9.9 # https://github.com/python273/vk_api
+certifi>=2023.7.22 # not directly required, pinned by Snyk to avoid a vulnerability
+pyjwt>=2.4.0 # not directly required, pinned by Snyk to avoid a vulnerability
+requests>=2.31.0 # not directly required, pinned by Snyk to avoid a vulnerability