doc(timeline): tweak comment in pagination to explain why it's correct

crates/matrix-sdk-ui/src/timeline/pagination.rs

@@ -41,8 +41,11 @@ impl super::Timeline {
                     );
                 }
                 None => {
-                    // TODO: returning `false` is not true everytime, we need a way to know if
-                    // lazy-loading has reached the end of the timeline.
+                    // We could adjust the skip count to a lower value, while passing the requested
+                    // number of events. We *may* have reached the start of the timeline, but since
+                    // we're fulfilling the caller's request, assume it's not the case and return
+                    // false here. A subsequent call will go to the `Some()` arm of this match, and
+                    // cause a call to the event cache's pagination.
                     return Ok(false);
                 }
             }