Graph: Improve point rendering performance (#22610)

this PR improves canvas rendering performance in drawSeriesPoints

public/vendor/flot/jquery.flot.js

@@ -2621,8 +2621,8 @@ Licensed under the MIT license.
                         ctx.fillStyle = fillStyle;
                         ctx.fill();
                     }
-                    ctx.stroke();
                 }
+                ctx.stroke();
             }
 
             ctx.save();