fix: doc-requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-IDNA-6597975

doc-requirements.txt

@@ -25,7 +25,7 @@ docutils==0.17.1
     #   sphinx-panels
 furo @ git+https://github.com/flyteorg/furo@main
     # via -r doc-requirements.in
-idna==3.6
+idna==3.7
     # via requests
 imagesize==1.4.1
     # via sphinx