Fix broken references

* "Unit of related browsing contexts" was removed from the HTML spec in 2019 (whatwg/html#4350)

* "Report task end time" moved to LONG-ANIMATION-FRAMES and has been renamed "Record task end time"

index.bs

@@ -47,7 +47,7 @@ urlPrefix: https://html.spec.whatwg.org/multipage/; spec: HTML;
     type: dfn; url: #calling-scripts; text: calling scripts;
     type: dfn; url: #list-of-the-descendant-browsing-contexts; text: list of the descendant browsing contexts;
     type: dfn; url: #ancestor-browsing-context; text: ancestor;
-    type: dfn; url: #unit-of-related-browsing-contexts; text: unit of related browsing contexts
+    type: dfn; url: #browsing-context-group-set; text: browsing-context-group-set
     type: dfn; url: #script-evaluation-environment-settings-object-set; text: script evaluation environment settings object set
     type: dfn; url: #integration-with-the-javascript-agent-cluster-formalism; text: agent cluster
     type: dfn; url: #concept-task-document; for: task; text: document;
@@ -230,7 +230,7 @@ Pointing to the culprit {#sec-PointingToCulprit}
 
 <em>This section is non-normative.</em>
 
-A <a>long task</a> can involve different types of work (such as script, layout, style etc), and it could be executed within different <a>browsing contexts</a>, or it could be global in nature such as a long garbage collection that spans the entire <a>agent cluster</a> or <a>unit of related browsing contexts</a>.
+A <a>long task</a> can involve different types of work (such as script, layout, style etc), and it could be executed within different <a>browsing contexts</a>, or it could be global in nature such as a long garbage collection that spans the entire <a>agent cluster</a> or <a>browsing context group set</a>.
 
 Thus <a>attribution</a> has a couple of facets:
 
@@ -294,7 +294,7 @@ Report long tasks {#report-long-tasks}
 <div algorithm="Report long tasks">
     Given |start time|, |end time|, |top-level browsing contexts|, and |task|, perform the following algorithm:
 
-    1. [=Report task end time=] given |end time| and |task|'s [=task/document=].
+    1. [=Record task end time=] given |end time| and |task|'s [=task/document=].
 
     1. If |end time| minus |start time| is less than the long tasks threshold of 50 ms, abort these steps.
 
@@ -456,4 +456,4 @@ The following are the timing attacks considered:
     the permalink page can be used to determine whether the user is in the target demographic.
 
 These scenarios are addressed by the 50ms threshold AND respecting cross-origin boundary i.e. not
-showing task type or additional attribution to untrusted cross origin observers.
+showing task type or additional attribution to untrusted cross origin observers.