Maintenance - Fix tests

[adranka]

Just some maintenance:

1. Change an equality check to an approx check so tests pass
2. Update some MvNormal calls based on the deprecation warning
3. Bump AutoHashEquals compat
4. Changed one of the methods of KeyedDistribution from this type signature:
   kd::KeyedDistribution, keys::Tuple{Vararg{AbstractVector{T} where T,N} where N}
   to
   kd::KeyedDistribution, keys::Tuple{Vararg{AbstractVector}}
   I believe these are equivalent:

julia> Tuple{Vararg{AbstractVector{T} where T, N} where N} === Tuple{Vararg{AbstractVector}}
true

And it removes another dep warning.