applets/clocks: Fix clocks tooltips

Reason for the change

If the system is set to a non-English locale, like Italian, the weekday names may be formatted in lowercase, and so they won't look good as titles or headings. This fix makes sure that the first character of the clocks' tooltips is always uppercase. In addition, a minor bug that printed twice the weekday name in the digital clock tooltip has been fixed too.

Screenshots or screen recordings

Before	After