sched/proxy: Remove superfluous clear_task_blocked_in()

Per the discussion here:

  https://lore.kernel.org/all/20260403112810.GG3738786@noisy.programming.kicks-ass.net/

The reason for this condition is that the signal condition in
try_to_block_task() would set_task_blocked_in_waking(). However, it no longer
does that, in fact, that path does clear_task_blocked_on().

Further, per the discussions here:

  https://lore.kernel.org/r/dc61cf77-e541-441d-a708-c40e19aa0db2%40amd.com
  https://lore.kernel.org/r//9dd1d24d-45d3-4ee2-8e67-8305b34bfb6d%40amd.com

there are a few other edge cases that needed this. But they're all
variants of PROXY_WAKING leaking out. And since PROXY_WAKING is now
gone, this is no longer needed either.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: John Stultz <jstultz@google.com>
Link: https://patch.msgid.link/20260526113322.120970670%40infradead.org

Author: Peter Zijlstra

kernel/sched/core.c

@@ -7142,9 +7142,6 @@ static void __sched notrace __schedule(int sched_mode)
 	if (sched_proxy_exec()) {
 		struct task_struct *prev_donor = rq->donor;
 
-		if (!prev_state && prev->blocked_on)
-			clear_task_blocked_on(prev, NULL);
-
 		rq_set_donor(rq, next);
 		next->blocked_donor = NULL;
 		if (unlikely(next->is_blocked)) {