games/sulis: Fix west road elevation

Backported patch [1] for upstream issue #221 [2], which blocks act3
campaign (fix west road elevation).

[1] https://github.com/Grokmoo/sulis/commit/fda9fbe830c0db6fbba153f3c2de34ccebf4630f?diff=unified&w=0
[2] https://github.com/Grokmoo/sulis/issues/221

PR: 283874
MFH: 2025Q1