Don't refill zone from external change.

We may later add an Automatic Zone Fill option which would restore
this, but for now I'm turning it off to see if it fixes the crash
bug.

Fixes: lp:1834718
* https://bugs.launchpad.net/kicad/+bug/1834718

pcbnew/tools/point_editor.cpp

@@ -1160,7 +1160,6 @@ int POINT_EDITOR::removeCorner( const TOOL_EVENT& aEvent )
 
 int POINT_EDITOR::modifiedSelection( const TOOL_EVENT& aEvent )
 {
-    m_refill = true;  // zone has been modified outside the point editor tool
     updatePoints();
     return 0;
 }