f - Gate Future::wait_timeout doc links on std

Now that `get_async_receive_offer_ready_future` and
`await_async_receive_offer` are available in no-std, their rustdoc
intra-doc links to `Future::wait_timeout` (which is itself still
std-only) break the no-std rustdoc build. Wrap the sentence and
reference definition that mention `Future::wait_timeout` in
`cfg_attr(feature = "std", doc = ...)` so the links only appear when
they can resolve.

Co-Authored-By: HAL 9000

Author: tnull

lightning/src/ln/channelmanager.rs

@@ -5888,11 +5888,17 @@ impl<
 	/// protocol completes, or immediately if one is already available.
 	///
 	/// Callers that need a timeout can combine this future with their runtime's timeout
-	/// primitive. Synchronous callers should instead fetch the underlying [`Future`] via
-	/// [`Self::get_async_receive_offer_ready_future`] and call [`Future::wait_timeout`] on it.
+	/// primitive.
+	#[cfg_attr(
+		feature = "std",
+		doc = "Synchronous callers should instead fetch the underlying [`Future`] via [`Self::get_async_receive_offer_ready_future`] and call [`Future::wait_timeout`] on it."
+	)]
 	///
 	/// [`Future`]: crate::util::wakers::Future
-	/// [`Future::wait_timeout`]: crate::util::wakers::Future::wait_timeout
+	#[cfg_attr(
+		feature = "std",
+		doc = "[`Future::wait_timeout`]: crate::util::wakers::Future::wait_timeout"
+	)]
 	pub async fn await_async_receive_offer(&self) -> Result<Offer, ()> {
 		if let Ok(offer) = self.get_async_receive_offer() {
 			return Ok(offer);

lightning/src/offers/flow.rs

@@ -1724,9 +1724,13 @@ impl<MR: MessageRouter, L: Logger> OffersMessageFlow<MR, L> {
 	/// Returns a [`Future`] that completes when an async receive offer is ready, i.e., after the
 	/// interactive static-invoice protocol completes.
 	///
-	/// Callers can either `.await` the returned [`Future`] in an async context or call
-	/// [`Future::wait_timeout`] from a synchronous context. After it completes, use
-	/// [`Self::get_async_receive_offer`] to retrieve the offer.
+	/// Callers can `.await` the returned [`Future`] in an async context.
+	#[cfg_attr(
+		feature = "std",
+		doc = "Synchronous callers can instead call [`Future::wait_timeout`] on it."
+	)]
+	///
+	/// After it completes, use [`Self::get_async_receive_offer`] to retrieve the offer.
 	pub fn get_async_receive_offer_ready_future(&self) -> Future {
 		self.async_receive_offer_ready_notifier.get_future()
 	}