Update SCons 4.8.1 to 4.9.1 (#18069)
Summary of the issue:
Update SCons from 4.8.1 to 4.9.1 to apply the latest security fixes.
https://github.com/SCons/scons/releases/tag/4.9.1
Description of user facing changes
none
Description of development approach
The Scons version in pyproject.toml and uv.lock has been updated to the latest stable version 4.9.1.
