Remove obsolete second wakeup_paused

It was introduced in d5822af.
If I understand it correctly this was done to prevent calling select
without timeout while there were pending paused promises.

Since now we explicitely check for this condition and call select with
zero timeout (`should_block_waiting_for_io`). This extra `wakeup_paused`
seems to be obsolete.

src/unix/lwt_main.ml

@@ -26,8 +26,6 @@ let abandon_yielded_and_paused () =
 
 let run p =
   let rec run_loop () =
-    (* Fulfill paused promises now. *)
-    Lwt.wakeup_paused ();
     match Lwt.poll p with
     | Some x ->
       x
@@ -40,7 +38,7 @@ let run p =
         Lwt.paused_count () = 0 && Lwt_sequence.is_empty yielded in
       Lwt_engine.iter should_block_waiting_for_io;
 
-      (* Fulfill paused promises again. *)
+      (* Fulfill paused promises. *)
       Lwt.wakeup_paused ();
 
       (* Fulfill yield promises. *)