fix(doc): remove misleading comment on last submitted height field (#967

)

block/manager.go

@@ -59,7 +59,7 @@ type Manager struct {
 		Submission
 	*/
 	// The last height which was submitted to both sublayers, that we know of. When we produce new batches, we will
-	// start at this height + 1. Note: only accessed by one thread at a time so doesn't need synchro.
+	// start at this height + 1.
 	// It is ALSO used by the producer, because the producer needs to check if it can prune blocks and it wont'
 	// prune anything that might be submitted in the future. Therefore, it must be atomic.
 	LastSubmittedHeight atomic.Uint64