fix: vendor/assets/components/bootstrap-datepicker/docs/requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-URLLIB3-7267250

Author: snyk-bot

vendor/assets/components/bootstrap-datepicker/docs/requirements.txt

@@ -1,3 +1,4 @@
 sphinx_rtd_theme
 pygments>=2.7.4 # not directly required, pinned by Snyk to avoid a vulnerability
 sphinx>=3.0.4 # not directly required, pinned by Snyk to avoid a vulnerability
+urllib3>=2.2.2 # not directly required, pinned by Snyk to avoid a vulnerability