Don't reevaluate at__MODULE__

[serenity4]

I realized that #131 does not actually fix the issue on nightly (and was tricked into believing it did by a faulty setup 🤦). The issue is caused by this behavior:

julia> let; global mod = Module()
           println(isdefined(mod, Symbol("@xx")))
           Core.eval(mod, :(macro xx() end))
           println(isdefined(mod, Symbol("@xx")))
       end
false
true

julia> isdefined(mod, Symbol("@xx"))
true

julia> let; global mod = Module()
           println(isdefined(mod, Symbol("@__MODULE__")))
           Core.eval(mod, :(macro __MODULE__() end))
           println(isdefined(mod, Symbol("@__MODULE__")))
       end
false # <- this used to return `true` on 1.11
false

julia> isdefined(mod, Symbol("@__MODULE__"))
true

which I believe was introduced by JuliaLang/julia#57253. Invoking isdefined with invokelatest gives the correct answer.

This is a simple temporary fix, but perhaps this should be fixed upstream. cc @Keno