Revert "[release-19.0] VTTablet: smartconnpool: notify all expired wa…

…iters (vitessio#16897) (vitessio#16901)"

This reverts commit 805d607.

go/pools/smartconnpool/waitlist.go

@@ -88,14 +88,11 @@ func (wl *waitlist[C]) expire(force bool) {
 	// or remove everything if force is true
 	for e := wl.list.Front(); e != nil; e = e.Next() {
 		if force || e.Value.ctx.Err() != nil {
+			wl.list.Remove(e)
 			expired = append(expired, e)
 			continue
 		}
 	}
-	// remove the expired waiters from the waitlist after traversing it
-	for _, e := range expired {
-		wl.list.Remove(e)
-	}
 	wl.mu.Unlock()
 
 	// once all the expired waiters have been removed from the waitlist, wake them up one by one