Add upper bound to GAPTypes dependency

[fingolfin]

On JuliaRegistries/General#5422 we were told:

The following dependencies do not have a compat entry that has an upper bound: GAPTypes

[ThomasBreuer]

Currently GAPTypes.jl has version "1.0.0".
We could be very conservative in the sense that any change in GAPTypes.jl will likely be incompatible, and will require a new release of GAP.jl.
If I understand the documentation in Pkg.jl right then we can express this as follows.

[compat]
GAPTypes = "= 1.0.0"

[fredrikekre]

Bump for JuliaRegistries/General#5422. I would recommend:

[compat]
GAPTypes = "1"

if you are following semantic versioning.