router: rhMarkObstacles should return a correct error status

Long story short: a few days ago I fixed error handling in routeStep(), so it actually started to recognize the wrong error status returned
by rhMarkObstacles() and think that the trace is always incorrect.

fixes: https://gitlab.com/kicad/code/kicad/-/issues/8557

pcbnew/router/pns_line_placer.cpp

@@ -695,7 +695,7 @@ bool LINE_PLACER::rhMarkObstacles( const VECTOR2I& aP, LINE& aNewHead )
 
     aNewHead = m_head;
 
-    return static_cast<bool>( m_currentNode->CheckColliding( &m_head ) );
+    return true;
 }