Fix sce update failure on Windows

[adarshm11]

Problem

PowerShell attempted to overwrite the current sce.exe executable during the execution of sce update, which resulted in the error "The process cannot access the file C:\...\sce.exe because it is being used by another process".

The Fix

Now, the update is scheduled to execute after sce update exits, so the current sce.exe is not overwritten mid-process.

Testing

This has not been tested yet on a Windows machine. Once tested, this description will be updated.