change pencil brush finalize to be in line with other brushes (fabric…

…js#5866)

src/brushes/pencil_brush.class.js

@@ -280,7 +280,7 @@
       var path = this.createPath(pathData);
       this.canvas.clearContext(this.canvas.contextTop);
       this.canvas.add(path);
-      this.canvas.renderAll();
+      this.canvas.requestRenderAll();
       path.setCoords();
       this._resetShadow();