fix: requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-URLLIB3-14192442
- https://snyk.io/vuln/SNYK-PYTHON-URLLIB3-14192443

Author: snyk-io[bot]

requirements.txt

@@ -22,3 +22,4 @@ tweepy
 # yulewalker  # uncomment once audio_filters/equal_loudness_filter.py is fixed
 typing_extensions
 xgboost
+urllib3>=2.6.0 # not directly required, pinned by Snyk to avoid a vulnerability