Loosen the version restrictions on GAP_pkg_juliainterface_jll

[fingolfin]

The goal was to ensure that we only pair versions of GAP.jl and GAP_pkg_juliainterface_jll which use matching C code. But sometimes rebuild or minor updates necessary. So I think we should loosen this here, and just be very careful about how we version GAP_pkg_juliainterface_jll.

The primary reason for the strict syncing of the C code is that we don't want our fallback code to kick in which re-compiles JuliaInterface.so from scratch if we notice that the C code deviates from the JLL. I guess we should make that code more robust by turning off that logic if GAP.jl is not dev'ed (and then just print a warning about the difference, but still proceed with crossed fingers). The same then would be used in Singular.jl (see oscar-system/Singular.jl#639 -- BTW @benlorenz if you have any feedback on that PR, I'd still be interested)