Unskip loaf-source-location-redirect and deflake

Sometimes the LoAFs have a slightly lower duration, be more
forgiving (utils.js already does this).

Bug: 1507152
Change-Id: I8ea49a581d65fcd5cb19f4c8bbd5911d8f7eaac8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5233107
Reviewed-by: Michal Mocny <mmocny@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1251598}

long-animation-frame/tentative/loaf-source-location-redirect.html

@@ -47,7 +47,7 @@ <h1>Long Animation Frame: source location with cross-origin redirects</h1>
           script.crossOrigin = "anonymous";
         document.body.appendChild(script);
         t.add_cleanup(() => script.remove());
-      }, script => script.duration >= VERY_LONG_FRAME_DURATION, t);
+      }, script => script.duration >= VERY_LONG_FRAME_DURATION - 5, t);
 
       const result =
         script.sourceLocation.startsWith(postRedirectURL) ? "post-redirect" :