doc: fix comments on spans

src/lib.rs

@@ -363,14 +363,14 @@ impl<Types: IpfsTypes> UninitializedIpfs<Types> {
  // the "current" span which is not entered but the awaited futures are instrumented with it
  let init_span = tracing::trace_span!(parent: &root_span, "init");
 
- // stored in the Ipfs, added on every method call
+ // stored in the Ipfs, instrumenting every method call
  let facade_span = tracing::trace_span!("facade");
 
  // stored in the executor given to libp2p, used to spawn at least the connections,
  // instrumenting each of those.
  let exec_span = tracing::trace_span!(parent: &root_span, "exec");
 
- // stored in the IpfsFuture, the background task.
+ // instruments the IpfsFuture, the background task.
  let swarm_span = tracing::trace_span!(parent: &root_span, "swarm");
 
  repo.init().instrument(init_span.clone()).await?;