The Skype developers have published an updated snap in the insider/stable channel for wider testing.
Version 8.51.76.61 can be installed via:-
snap install skype --channel=insider/stable
Or, if you already have it installed, you can switch to the insider/stable channel via:-
snap refresh skype --channel=insider/stable
See also Skype Snap is out-of-date and Is the Skype Snap Still Maintained?