doc: mistakes in example script

https://doc.qt.io/qtinstallerframework/ifw-updates.html#promoting-updates-for-the-maintenance-tool

The example script "installscript.qs" provided at above URL has a couple of mistakes:

The version switch: the comments say "as of 4.8.1", but the if checks "before 4.8.0". I have 4.8.0. This resulted in a rather odd error message:

[54326] Started
[54744] Operation \"Extract\" with arguments \"installer://maintenancetool/4.8.0maintenancetool.app.7z; /tmpMaintenanceToolApp\" failed: Error while extracting archive \"installer://maintenancetool/4.8.0maintenancetool.app.7z\": Not enough memory
[54744] installationErrorWithCancel : Installer Error : Error during installation process (maintenancetool):
Error while extracting archive "installer://maintenancetool/4.8.0maintenancetool.app.7z": Not enough memory Retry|Ignore|Cancel

I changed the check to "<4.8.1" , then got ...

[11622] Warning: The current maintenance tool could not be updated. "/maintenancetool.app" does not exist. Please fix the "setInstallerBaseBinary(<temp_installer_base_binary_path>)" call in your script.

It took me some time to note the missing TargetDir prefix in the message, but after replacing all uses of @TargetDir@ with installer.value("TargetDir") + "..." it finally worked as expected.