Revert of [SVG] Implement 'discard' element

LayoutTests/svg/animations/discard-rect-with-anim-child-a.svg

Index: LayoutTests/svg/animations/discard-rect-with-anim-child-a.svg
diff --git a/LayoutTests/svg/animations/discard-rect-with-anim-child-a.svg b/LayoutTests/svg/animations/discard-rect-with-anim-child-a.svg
deleted file mode 100644
index 987489b60716bda19dfd47e33199b2732d9aae5c..0000000000000000000000000000000000000000
--- a/LayoutTests/svg/animations/discard-rect-with-anim-child-a.svg
+++ /dev/null
@@ -1,21 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<svg onload="loaded()" version="1.2" baseProfile="tiny" id="svg-root" width="100%" height="100%"
-  viewBox="0 0 480 360" xmlns="http://www.w3.org/2000/svg"
-  xmlns:xlink="http://www.w3.org/1999/xlink">
-  <rect id="r1" x="100" y="100" width="200" height="200" fill="green"/>
-  <rect id="r2" x="100" y="100" width="200" height="200" fill="blue">
-    <set attributeName="fill" to="red" begin="2s" fill="freeze" />
-    <discard id="discard1" begin="4s"/>
-  </rect>
-  <script>
-    if (window.testRunner)
-      testRunner.waitUntilDone();
-
-    function loaded() {
-      document.documentElement.setCurrentTime(4);
-
-      if (window.testRunner)
-        setTimeout(function(){testRunner.notifyDone();}, 10);
-    }
-  </script>
-</svg>