Display polkit in translated texts

[ryonakano]

Before

The description text in the Polkit dialog "Authentication is required to manage locale settings" is not shown as translated.

After

Moving the translation domain of the policy file, now the text is shown as translated in the user language.

[tintou]

You might want to try https://github.com/elementary/switchboard-plug-locale/pull/162 instead

[ryonakano]

Superseded by #162