I'm pretty sure OP is referring to the liftgate beeping sound.
There's a small middle speaker in the liftgate trim that has a white connector. Disconnect that and you're good.
I believe you can just pop out the speaker grill and then unclip it.
Here's an unrelated thread post but it shows what I'm talking about:
Recontenting the speakers in the rear hatch?
Another option if you're already taking apart the liftgate is by disconnecting the wire from the other side. Check out the video below and you can see the white connector at the 7:05 mark.
Good luck.