removed unnecessary imports

Author: mstr2

modules/javafx.graphics/src/main/java/javafx/scene/layout/BorderStroke.java

@@ -30,9 +30,7 @@
 import javafx.beans.NamedArg;
 import javafx.geometry.Insets;
 import javafx.scene.paint.Color;
-import javafx.scene.paint.LinearGradient;
 import javafx.scene.paint.Paint;
-import javafx.scene.paint.RadialGradient;
 import javafx.scene.shape.StrokeType;
 import java.util.Objects;