fix: requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-MYSQLCONNECTORPYTHON-9724724

Author: snyk-bot

requirements.txt

@@ -18,7 +18,7 @@ typing-extensions>=3.7.4.2
 urllib3>=1.25.10
 websockets>=8.1
 yarl>=1.5.1
-mysql-connector-python>=8.0.21
+mysql-connector-python>=9.3.0
 alt-profanity-check==1.1.3
 protobuf>=3.20.2 # not directly required, pinned by Snyk to avoid a vulnerability