fix: mcp/simple-python-fast-mcp/requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-PYTHONDOTENV-16115271

Author: snyk-io[bot]

mcp/simple-python-fast-mcp/requirements.txt

@@ -3,3 +3,4 @@ dotenv==0.9.9
 email_validator==2.2.0
 fastmcp==2.11.3
 pip==24.3.1
+python-dotenv>=1.2.2 # not directly required, pinned by Snyk to avoid a vulnerability