gcal-calendars-page: Minor tweaks to the AdwToast title

AdwToast title is already bold, so using HTML b tags doesn't do
anything. To fix this, use quote symbols instead.

And:
- Use the quote symbols recommended by HIG:
https://developer.gnome.org/hig/guidelines/typography.html#take-advantage-of-unicode
- Add a translator comment explaining what "%s" means

src/gui/calendar-management/gcal-calendars-page.c

@@ -353,7 +353,9 @@ gcal_calendars_page_activate (GcalCalendarManagementPage *page,
   remove_calendar (self, calendar);
 
   /* Create the new toast */
-  new_string = g_markup_printf_escaped (_("Calendar <b>%s</b> removed"),
+
+  /* TRANSLATORS: %s is a calendar name. */
+  new_string = g_markup_printf_escaped (_("Calendar “%s” removed"),
                                         gcal_calendar_get_name (calendar));
 
   toast = adw_toast_new (new_string);