qt: remove colon in "Payment received" notification

if there is no amount in the payment request the notification would look
weird as it would just show `Payment received:` indicating something
might be missing. Now it just says `Payment received` instead.

Author: f321x

electrum/gui/qt/main_window.py

@@ -1357,10 +1357,10 @@ def on_event_request_status(self, wallet, key, status):
             return
         if status == PR_PAID:
             # FIXME notification should only be shown if request was not PAID before
-            msg = _('Payment received:')
+            msg = _('Payment received')
             amount = req.get_amount_sat()
             if amount:
-                msg += ' ' + self.format_amount_and_units(amount)
+                msg += ': ' + self.format_amount_and_units(amount)
             msg += '\n' + req.get_message()
             self.notify(msg)
             self.receive_tab.request_list.delete_item(key)