Update requirements.txt (#999)

Update to latest mapscript version

Co-authored-by: Seth G <[email protected]>

Author: github-actions[bot]

requirements.txt

@@ -4,4 +4,4 @@ sphinx==8.1.3
 sphinx-copybutton==0.5.2
 sphinxcontrib-jquery==4.1
 --extra-index-url https://test.pypi.org/simple/
-mapscript==8.2.2
+mapscript==8.4.0