OPSD Skardu riverbed banks fix

This add-on addresses rendering issues in the OPSD Skardu area by fixing the riverbed appearance. Water was previously displaying across the entire width of the riverbed, creating an illusion of a shallow lake. The update includes water exclusion polygons that restore the realistic look of dry sand and gravel banks. Compatible with various airport sceneries, this fix is designed for FS2024 users, with project files available for authors wishing to incorporate the fixes.