avoid setting modality in progress dialog

when modal, the program hangs on OS X when moving back and forth
between the main window and the profile manager, and I haven't been able
to find a better workaround

.update() ignores user input when processing events, so this will
hopefully not break things

aqt/progress.py

@@ -112,7 +112,6 @@ class ProgressManager:
         self._win.setCancelButton(None)
         self._win.setAutoClose(False)
         self._win.setAutoReset(False)
-        self._win.setWindowModality(Qt.ApplicationModal)
         self._win.setMinimumWidth(300)
         # we need to manually manage minimum time to show, as qt gets confused
         # by the db handler