Remove layout tests that run execCommand on non-HTML documents

LayoutTests/svg/custom/delete-modified-text-in-defs-crash.svg

Index: LayoutTests/svg/custom/delete-modified-text-in-defs-crash.svg
diff --git a/LayoutTests/svg/custom/delete-modified-text-in-defs-crash.svg b/LayoutTests/svg/custom/delete-modified-text-in-defs-crash.svg
deleted file mode 100644
index 9573f35171eb1a0e3f607d1d4ba86377b60cf05f..0000000000000000000000000000000000000000
--- a/LayoutTests/svg/custom/delete-modified-text-in-defs-crash.svg
+++ /dev/null
@@ -1,29 +0,0 @@
-<svg id="svgRoot" xmlns="http://www.w3.org/2000/svg" onload="go()">
-  <defs>
-    <text>
-      <tspan id="tspan1" x="375"></tspan>
-      <tspan>PASS</tspan>
-    </text>
-  </defs>
-  <g><rect id="legendbox"/></g>
-  <script><![CDATA[
-    document.execCommand("SelectAll");
-    elem = document.getElementById("tspan1");
-    elem.removeAttribute("x");
-    range = document.createRange();
-    range.setStartBefore(document.getElementById("tspan1"));
-    range.setEndAfter(document.getElementById("legendbox"));
-    range.deleteContents();
-
-    if (window.testRunner)
-        testRunner.dumpAsText();
-
-    function go() {
-      var svgRoot = document.getElementById("svgRoot");
-      var passText = document.createElementNS("http://www.w3.org/2000/svg", "text");
-      var textContent = document.createTextNode("PASS");
-      passText.appendChild(textContent);
-      svgRoot.appendChild(passText);
-    }
-  ]]></script>
-</svg>