fix: requirements/docs.txt to reduce vulnerabilities

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

requirements/docs.txt

@@ -120,7 +120,7 @@ furo==2022.12.7 \
     --hash=sha256:7cb76c12a25ef65db85ab0743df907573d03027a33631f17d267e598ebb191f7 \
     --hash=sha256:d8008f8efbe7587a97ba533c8b2df1f9c21ee9b3e5cad0d27f61193d38b1a986
     # via -r requirements/docs.in
-idna==3.4 \
+idna==3.7 \
     --hash=sha256:814f528e8dead7d329833b91c5faa87d60bf71824cd12a7530b5526063d02cb4 \
     --hash=sha256:90b77e79eaa3eba6de819a0c442c0b4ceefc341a7a2ab77d7562bf49f425c5c2
     # via requests