[Pushed] Installer translation problems

[chack1172]

I was translating the install/upgrade wizard in italian and I saw that some strings couldn't be trasnlated from the language file.

I edited it in my github fork and send a pull request to the mybb's repository if you want to add it.
Fork Commit: https://github.com/chack1172/mybb/commit...10ee8d7780
Pull Request: https://github.com/mybb/mybb/pull/2627

[Eldenroot]

This should be pushed if we wanna include this into MyBB, PR is available on GitHub.
https://github.com/mybb/mybb/pull/2627