Fixed the timing to disable the slide effect

rust/pyxel-engine/src/channel.rs

@@ -104,7 +104,7 @@ impl Channel {
                 self.note_index += 1;
             }
             while self.note_index >= sound.notes.len() as u32 {
-                self.is_first_note = false;
+                self.is_first_note = true;
                 self.sound_index += 1;
                 self.note_index = 0;
                 if self.sound_index >= self.sounds.len() as u32 {