BUILD: mux-h2: fix typo breaking build when using DEBUG_LOCK

A typo was accidently introduced in commit 48ce6a3 ("BUG/MEDIUM: muxes:
Make sure nobody stole the connection before using it."), a "&" was
placed in front of "OTHER_LOCK", which breaks DEBUG_LOCK. No backport
is needed.
diff --git a/src/mux_h2.c b/src/mux_h2.c
index 08120e9..beaf1a1 100644
--- a/src/mux_h2.c
+++ b/src/mux_h2.c
@@ -3714,7 +3714,7 @@
 		 */
 		if (!t->context) {
 			h2c = NULL;
-			HA_SPIN_UNLOCK(&OTHER_LOCK, &idle_conns[tid].takeover_lock);
+			HA_SPIN_UNLOCK(OTHER_LOCK, &idle_conns[tid].takeover_lock);
 			goto do_leave;
 		}