`effect_free` still not inferred for `Memory`

[nsajko]

Fixed for Vector (#33), but not for Memory:

julia> using Collects

julia> f(x) = collect_as(Vector, x)
f (generic function with 1 method)

julia> g(x) = collect_as(Memory, x)
g (generic function with 1 method)

julia> Base.infer_effects(f, Tuple{typeof((n*n for n ∈ 1:3))})
(!c,+e,!n,!t,+s,!m,+u,+o,+r)

julia> Base.infer_effects(g, Tuple{typeof((n*n for n ∈ 1:3))})
(!c,!e,!n,!t,+s,!m,!u,+o,!r)