Add a unique test for event.path removal (#32351)

This is purely to work around the limitation that the Interop-2022
tooling can't work with subtests, and can be removed once that is no
longer relevant, in favour of the test in historical.html.
diff --git a/dom/eventPathRemoved.html b/dom/eventPathRemoved.html
new file mode 100644
index 0000000..7a69539
--- /dev/null
+++ b/dom/eventPathRemoved.html
@@ -0,0 +1,16 @@
+<!DOCTYPE html>
+<title>Event.path must be removed</title>
+<!-- Note that this duplicates a test in historical.html for the purposes of
+     using in the Interop-2022 metric -->
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<div id=log></div>
+<script>
+test(() => {
+    const name = "path";
+    assert_false(name in Event.prototype)
+    assert_equals(Event.prototype[name], undefined)
+    assert_false(name in new Event("test"))
+    assert_equals((new Event("test"))[name], undefined)
+  }, "Event.prototype should not have this property: " + name)
+</script>