Fix validation in SPI package list

Our package list validation runs on Linux, which prevents this package from being added:

Package.swift

@@ -7,7 +7,7 @@ import PackageDescription
 let excludeFiles = [
     "./Browser/BrowserViewController.swift" // Because of inheriting iOS only class failed to build on macOS.
 ]
-#elseif os(iOS)
+#else
 let excludeFiles: String = []
 #endif