[TRIVIAL] Add implementation detail reminder for the settlement queue (…

…#3240)

~~Seems like it was overlooked in
#3129. `/solve` requests
must not be sent in case the settlement queue for the current solver is
out of capacity.~~ Adds a comment as a reminder that the queue needs to
be checked only **after** the solve response is received.

crates/driver/src/infra/api/routes/solve/mod.rs

@@ -37,6 +37,8 @@ async fn route(
             .prioritize(auction, &competition.solver.account().address())
             .await;
         let result = competition.solve(auction).await;
+        // Solving takes some time, so there is a chance for the settlement queue to
+        // have capacity again.
         competition.ensure_settle_queue_capacity()?;
         observe::solved(state.solver().name(), &result);
         Ok(axum::Json(dto::SolveResponse::new(