add show for typed comprehension expressions

```julia
# Before
julia> :(Int[i for (i, j) in zip(1:10, 1:10)])
:($(Expr(:typed_comprehension, :Int, :i, :((i,j) = zip(1:10,1:10)))))

# After
julia> :(Int[i for (i, j) in zip(1:10, 1:10)])
:(Int[i for (i,j) = zip(1:10,1:10)])
```