Browsing Italian translation

Fix the label width at the maximum necessary for the plural labels, to prevent it changing size when we change the spinner value
Translators: you should translate this string to a number (written in digits) which corresponds to the longer character length of the
* translations for "second" and "seconds", as translated elsewhere in this file. For example, in English, "second" is 6 characters long and
* "seconds" is 7 characters long, so this string should be translated to "7". See: bgo#639398