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/os2/os2.cpp

@@ -174,7 +174,7 @@ int CDECL main(int argc, char *argv[])
 	SetRandomSeed(time(nullptr));
 
 	/* 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]);
 
 	return openttd_main(argc, argv);
 }