Multichannel: fix polygon 'rectifying' function

It was choosing the wrong side of the boundary, which
caused it to sometimes self-intersect and omit some components.

Fixes: https://gitlab.com/kicad/code/kicad/-/issues/19068

pcbnew/tools/multichannel_tool.cpp

@@ -195,7 +195,7 @@ const SHAPE_LINE_CHAIN MULTICHANNEL_TOOL::buildRAOutline( std::set<FOOTPRINT*>&
         const VECTOR2I p1( seg.B.x, seg.A.y );
 
         raOutline.Append( seg.A );
-        if( hull.PointInside( p0 ) )
+        if( !hull.PointInside( p0 ) )
             raOutline.Append( p0 );
         else
             raOutline.Append( p1 );