De-flake toggleEvent.html

This patch removes the open attribute from some of the details elements
in the initial HTML markup because the timing at which the parser will
fire the toggle event is inconsistent and leads to test flaking.

Fixed: 1487880, 1488725
Change-Id: I623382108f8eaf9e43e07172133c5551926ae062
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4907762
Reviewed-by: David Baron <dbaron@chromium.org>
Commit-Queue: Joey Arhar <jarhar@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1204864}

html/semantics/interactive-elements/the-details-element/toggleEvent.html

@@ -10,7 +10,7 @@
   <summary>Lorem ipsum</summary>
   <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.</p>
 </details>
-<details id=details2 open>
+<details id=details2>
   <summary>Lorem ipsum</summary>
   <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.</p>
 </details>
@@ -28,7 +28,7 @@
   <summary>Lorem ipsum</summary>
   <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.</p>
 </details>
-<details id=details8 open>
+<details id=details8>
   <summary>Lorem ipsum</summary>
   <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.</p>
 </details>
@@ -88,6 +88,7 @@
     assert_false(details2.open);
     testEvent(evt);
   });
+  details2.open = true;
   details2.open = false; // closes details2
 
   details3.ontoggle = t3.step_func_done(function(evt) {
@@ -147,6 +148,7 @@
     assert_false(details8.open);
     testEvent(evt)
   });
+  details8.open = true;
   details8.removeAttribute('open'); // closes details8
 
   window.details9TogglePromise.then(t9.step_func(() => {