Remove Node#obscured? parameters

Although `Capybara::Selenium::Node#obscured?` accepts `x` and `y`
arguments, these parameters do not appear to part of the public Capybara
API.

Author: myabc

lib/capybara/cuprite/browser.rb

@@ -210,12 +210,8 @@ def path(node)
         evaluate_on(node: node, expression: "_cuprite.path(this)")
       end
 
-      def obscured?(node, x = nil, y = nil)
-        if x && y
-          evaluate_on(node: node, expression: "_cuprite.isObscured(this, #{x}, #{y})")
-        else
-          evaluate_on(node: node, expression: "_cuprite.isObscured(this)")
-        end
+      def obscured?(node)
+        evaluate_on(node: node, expression: "_cuprite.isObscured(this)")
       end
 
       def all_text(node)

lib/capybara/cuprite/javascripts/index.js

@@ -119,18 +119,13 @@ class Cuprite {
    * Returns true if the node is obscured in the viewport.
    *
    * @param {Element} node
-   * @param {number} [x] the center position
-   * @param {number} [y] the center position
    * @return {boolean} true if the node is obscured, false otherwise
    */
-  isObscured(node, x, y) {
+  isObscured(node) {
     let win = window;
     let rect = node.getBoundingClientRect();
-    x = x ?? rect.width / 2;
-    y = y ?? rect.height / 2;
-
-    let px = rect.left + x;
-    let py = rect.top + y;
+    let px = rect.left + rect.width / 2;
+    let py = rect.top + rect.height / 2;
 
     while (win) {
       let topNode = win.document.elementFromPoint(px, py);

lib/capybara/cuprite/node.rb

@@ -213,8 +213,8 @@ def path
         command(:path)
       end
 
-      def obscured?(x: nil, y: nil)
-        command(:obscured?, x, y)
+      def obscured?
+        command(:obscured?)
       end
 
       def inspect