[Backport branch-8-2] update Sphinx (#983)

* update Sphinx

* update Sphinx

* upgrade to 8.1.3

---------

Co-authored-by: Jeff McKenna <[email protected]>

Author: github-actions[bot]

requirements.txt

@@ -1,7 +1,7 @@
 alabaster==1.0.0
 docutils==0.21.2
-sphinx==8.0.2
+sphinx==8.1.3
 sphinx-copybutton==0.5.2
 sphinxcontrib-jquery==4.1
 --extra-index-url https://test.pypi.org/simple/
-mapscript==8.2.0
+mapscript==8.2.0