Remove deprecated window.showModalDialog()

ManualTests/show-modal-dialog-test.html

Index: ManualTests/show-modal-dialog-test.html
diff --git a/ManualTests/show-modal-dialog-test.html b/ManualTests/show-modal-dialog-test.html
deleted file mode 100644
index ec39ee44f3fdc00228833e15429713e12057bbd8..0000000000000000000000000000000000000000
--- a/ManualTests/show-modal-dialog-test.html
+++ /dev/null
@@ -1,15 +0,0 @@
-<script>
-function showModal() {
-    document.form.fromModal.value =
-        showModalDialog("modal-dialog.html",
-            document.form.toModal.value,
-            "dialogHeight:280px,dialogWidth:400px");
-}
-</script>
-<form name="form">
-<p>Type text here to be sent to the modal window and press the button:
-<input name="toModal" value="from main window">
-<input type="button" value="Show Modal" onClick="showModal()"></p>
-<hy>
-<p>Text will appear here from the modal window: <input name="fromModal">
-</form>