Fix statusicon tooltip

 * Don't use markup language on set_tooltip_text (as this function only
   accepts raw text), and for set_tooltip_markup use Pango markup language
   (different than HTML). So use a new-line character instead of <br>.

revolt/statusicon.py

@@ -138,9 +138,9 @@ def __init__(self, delegate, context_menu, app):
 
     def set_tooltip(self, text):
         if text is None:
-            self._icon.set_tooltip_text("<b>Revolt</b>")
+            self._icon.set_tooltip_text("Revolt")
         else:
-            self._icon.set_tooltip_markup("<b>Revolt</b><br>{!s}".format(text))
+            self._icon.set_tooltip_markup("<b>Revolt</b>\n{!s}".format(text))
 
     def set_status(self, status):
         if status is Status.BLINKING: