incorrect method lookup for Union{} type dispatch

[vtjnash]

julia> Base._methods_by_ftype(Tuple{Core.TypeofBottom, Vararg}, 5, Base.get_world_counter())
Any[]

julia> Type{Core.Union{}} == Core.TypeofBottom
true

julia> Base._methods_by_ftype(Tuple{Type{Core.Union{}}, Int}, 5, Base.get_world_counter())
1-element Vector{Any}:
 Core.MethodMatch(Tuple{Type{Union{}}, Int64}, svec(), Union{}(a...) @ Core boot.jl:321, true)

The Core.TypeofBottom probably often gets normalized to Type{Core.Union{}} so this doesn't get observed often, but I was noticing it leading to incorrect method invalidations during reloading.