syncscroll: Fix TypeError with Qt WebKit and Python 3.10

This fix is not needed in master branch because we do not support
Qt WebKit anymore.

Fixes #573.

ReText/syncscroll.py

@@ -134,6 +134,9 @@ def _updatePreviewScrollPosition(self):
         preview_scroll_offset = preview_pixel_to_scroll_to - distance_to_top_of_viewport
 
         pos = self.frame.scrollPosition()
+        # scrollPosition() returns QPoint for WebKit and QPointF for WebEngine
+        if isinstance(pos, QPoint):
+            preview_scroll_offset = int(preview_scroll_offset)
         pos.setY(preview_scroll_offset)
         self.frame.setScrollPosition(pos)