dateMenu: Format weather forecast times without AM/PM

If the clock is set to 12h, the AM/PM in the weather forecast times
should be clear from the context, because they are the immediately
following hours. This makes it less likely that the times will be
ellipsized (in which case the AM/PM wouldn't be shown anyway.)

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/835

js/ui/dateMenu.js

@@ -336,6 +336,7 @@ class WeatherSection extends St.Button {
             let [ok_, timestamp] = fc.get_value_update();
             let timeStr = Util.formatTime(new Date(timestamp * 1000), {
                 timeOnly: true,
+                ampm: false,
             });
 
             let icon = new St.Icon({ style_class: 'weather-forecast-icon',