Don't abort if already installed

[bersbersbers]

Description

I'd argue that if scoop is installed already, the installer should not abort since that would abort CI jobs.

Possible Solution

Exit gracefully here:

https://github.com/ScoopInstaller/Install/blob/656e17b67e8468edc5c5bd51bdad55642a03d9a4/install.ps1#L151-L154