fix: docs/requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-SETUPTOOLS-9964606

Author: snyk-bot

docs/requirements.txt

@@ -3,7 +3,7 @@ matplotlib>=3.7.3
 numpy>=1.24.4
 pybind11==2.4.3
 requests>=2.32.0 # not directly required, pinned by Snyk to avoid a vulnerability
-setuptools>=70.0.0
+setuptools>=78.1.1
 sphinx==5.3.0
 sphinx-gallery==0.8.1
 urllib3>=2.2.2 # not directly required, pinned by Snyk to avoid a vulnerability