chore(http/retry): add todo comments concerning eos

for now, a replaying body that will not yield trailers must be polled to
the `None` before reporting itself as reaching the end of the stream.

this isn't hugely important, but does affect some test control flow.

leave two todo comments so that if/when upgrading to hyper 1.0, it is
clear that these are not load-bearing or otherwise expected behavior,
should this behavior be rectified.

Signed-off-by: katelyn martin <[email protected]>

linkerd/http/retry/src/replay/tests.rs

@@ -358,6 +358,7 @@ async fn eos_only_when_fully_replayed() {
         .expect("yields a frame")
         .into_data()
         .expect("yields a data frame");
+    // TODO(kate): the replay doesn't report ending until it has (not) yielded trailers.
     assert!(replay.frame().await.is_none());
     assert!(replay.is_end_stream());
 
@@ -378,6 +379,7 @@ async fn eos_only_when_fully_replayed() {
         .expect("yields a frame")
         .into_data()
         .expect("yields a data frame");
+    // TODO(kate): the replay doesn't report ending until it has (not) yielded trailers.
     assert!(replay2.frame().await.is_none());
     assert!(replay2.is_end_stream());
 }