increase expected size of setup.ml to < 3kB

on my system, the generated setup.ml is 2602 bytes. with the recent changes
to add license headers, and other increases such as for OCAML_TOPLEVEL_PATH,
without corresponding increases in this size limit, I believe changing the
the expected test value is the correct fix.
Merge pull request #35 from adferguson/setup_size

increase expected size of setup.ml to < 3kB