Codechange: rename str_validate to StrMakeValid(InPlace) (#9304)

This to be more explicit the function changes the value, and not
returns yes/no.

src/os/windows/win32.cpp

@@ -429,7 +429,7 @@ int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLi
 	argc = ParseCommandLine(cmdline, argv, lengthof(argv));
 
 	/* Make sure our arguments contain only valid UTF-8 characters. */
-	for (int i = 0; i < argc; i++) ValidateString(argv[i]);
+	for (int i = 0; i < argc; i++) StrMakeValidInPlace(argv[i]);
 
 	openttd_main(argc, argv);