Contextualize "Public" website attribute translation string in Multisite settings

[audrasjb]

In wp-admin/network/site-info.php, the "Public" translation string should be contextualized, especially for languages were "public" can be masculine or feminine depending on context.

$attribute_fields = array( 'public' => __( 'Public' ) );
if ( ! $is_main_site ) {
	$attribute_fields['archived'] = __( 'Archived' );
	$attribute_fields['spam']     = _x( 'Spam', 'site' );
	$attribute_fields['deleted']  = __( 'Deleted' );
}

I'd suggest to contextualize this string, just as it is for the "Spam" translation string.

[SergeyBiryukov]

In 49962:

I18N: Add context for the Public string in site attributes list on Edit Site screen.

This allows for the string to be distinguished from a post status of the same name, which is useful for better translations in languages were "public" can be masculine or feminine depending on context.

Props audrasjb.
Fixes #52309.