gist for genus3.m needs to be updated

[AndrewVSutherland]

https://gist.github.com/edgarcosta/52eb0a8de56d78724be6c07f63ac2caa/29b0a6d1606bfce5959c2943198064c1fb954061#file-genus3-m is missing some semicolons and won't load with the latest version of Magma.

[AndrewVSutherland]

There is a published version at https://github.com/AndrewVSutherland/Genus3Covers/blob/main/genus3.m you could use that fixes this (but it does not implement all the intrinsics that are in the gist, only a subset).