BUILD: sched: fix build with DEBUG_THREAD with the previous commit

The build with DEBUG_THREAD was broken by commit fc50b9dd1 ("BUG/MAJOR:
sched: protect task during removal from wait queue"). It took me a while
to figure how to declare and aligned and initialized rwlock that wasn't
static, but it turns out that __decl_aligned_rwlock() does exactly this,
so that we don't have to assign an integer value when a struct is expected
in case of debugging.

No backport is needed.
diff --git a/src/task.c b/src/task.c
index 5d009fa..faf21f3 100644
--- a/src/task.c
+++ b/src/task.c
@@ -40,7 +40,7 @@
  * into another one. Storing the WQ index into the task doesn't seem to be
  * sufficient either.
  */
-__decl_thread(HA_RWLOCK_T wq_lock THREAD_ALIGNED(64) = 0);
+__decl_aligned_rwlock(wq_lock);
 
 /* Flags the task <t> for immediate destruction and puts it into its first
  * thread's shared tasklet list if not yet queued/running. This will bypass