Module-map xcframework headers excluded from HEADER_SEARCH_PATHS

Targets depending on a precompiled xcframework that ships its own module.modulemap no longer get a second copy of that module on HEADER_SEARCH_PATHS, ending the redefinition of module ‘X’ regression introduced in 4.201.0-rc.1. Xcode’s ProcessXCFramework already extracts those headers (including any module.map) into $(BUILT_PRODUCTS_DIR)/include, so the additional entry was redundant. Module-map-less xcframeworks (e.g. cached Swift/library products) still have their headers exposed as before.