Back out check-for-mouse-in-selection-bbox for PCBNew.

Unlike eeschema, PCBNew has had a selection model for two major
releases so folks have gotten used to RMB acting on the selection
rather than what's under the mouse.

Plus it makes RMB after a drag-select nearly useless as your mouse
by definition ends up outside the selection bbox.

Fixes https://gitlab.com/kicad/code/kicad/issues/5857

pcbnew/tools/selection_tool.cpp

@@ -245,10 +245,8 @@ int SELECTION_TOOL::Main( const TOOL_EVENT& aEvent )
         {
             bool selectionCancelled = false;
 
-            if( m_selection.Empty() ||
-                    !m_selection.GetBoundingBox().Contains( wxPoint( evt->Position() ) ) )
+            if( m_selection.Empty() )
             {
-                ClearSelection();
                 selectPoint( evt->Position(), false, &selectionCancelled );
                 m_selection.SetIsHover( true );
             }