It's giving you that/those error(s) because removing that object would leave the access-list empty but still existing, which is not possible or allowed, and you can't delete an access-list like that (by just saying "no" on its only line).
What you need to do is:
clear config access-list out2in
This will disassociate the access-list with the interface and ...
I'm taking a bit of a guess here.
ASA-4-713903: is a VPN peer misbehaving. With a follow on description.
In your case you are seeing discards due to packet size, related to the peer. I believe this is an Ikev2 Keepalive mis-match.
It appears that your end of the tunnel does not match their end of the tunnel for keepalive packets. Keepalives would be ...