doc: update stale FIXME into different FIXME

http/src/v0/refs.rs

@@ -468,8 +468,8 @@ fn iplds_refs<T: IpfsTypes>(
                     warn!("failed to load {}, linked from {}: {}", cid, source, e);
                     // TODO: yield error msg
                     // unsure in which cases this happens, because we'll start to search the content
-                    // and stop only when request has been cancelled (FIXME: not yet, because dropping
-                    // all subscriptions doesn't "stop the operation.")
+                    // and stop only when request has been cancelled (FIXME: no way to stop this
+                    // operation)
                     continue;
                 }
             };