Improve localization extension installation message

[joaomoreno]

Rephrase this to something like:

In order to use VS Code in German, VS Code needs to restart.

Have a single button:

Restart Now

We don't need a No button, since the notification can be dismissed.

[sandy081]

This message appears when a user installs a language and current message makes sense because it tells the user that there is a change in language is needed and not just restart. Saying just restart might be misleading the user.

In order to use VS Code in German, VS Code needs to restart makes sense if user configured to use German language and install the extension.

I would apply the above message in the second case and remove the No Button.