fix: rtd_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-bot

rtd_requirements.txt

@@ -12,4 +12,4 @@ donfig
 psutil
 setuptools>=65.5.1 # not directly required, pinned by Snyk to avoid a vulnerability
 requests>=2.32.2 # not directly required, pinned by Snyk to avoid a vulnerability
-urllib3>=2.5.0 # not directly required, pinned by Snyk to avoid a vulnerability
+urllib3>=2.6.0 # not directly required, pinned by Snyk to avoid a vulnerability