[6.15.z] Bump sphinx from 8.1.0 to 8.1.3 (#16662)

Bump sphinx from 8.1.0 to 8.1.3 (#16660)

(cherry picked from commit 043593f)

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

requirements-optional.txt

@@ -5,7 +5,7 @@ pre-commit==3.8.0
 ruff==0.6.9
 
 # For generating documentation.
-sphinx==8.1.0
+sphinx==8.1.3
 sphinx-autoapi==3.3.2
 
 # For 'manage' interactive shell