Gate inline-records-with-attributes test to >=4.03

[ELLIOTTCABLE]

Fixing #199 on 4.02.3. Somebody should sanity-check this; it was just the simplest way for me to get the tests passing. (hi! 🙋‍♀️ yep, that's me, still over here being an annoyance 🤣)

Presumably, whatever feature he's adding support for is unavailable on the 4.02-series? Nonetheless, being present in the tests-file at all breaks them on 4.02.3 for me:

    ocamlopt .ppx/20e3ffc6dc013e448ad889e12acbb4d5/ppx.exe
         ppx src_test/map/test_deriving_map.pp.ml
    ocamlopt src_test/deriving/test_ppx_deriving.exe
    ocamldep src_test/map/.test_deriving_map.eobjs/test_deriving_map.pp.ml.d
    ocamlopt .ppx/4c4b0dc849c26ef889ee6f55cb3a0672/ppx.exe
      ocamlc src_test/map/.test_deriving_map.eobjs/byte/test_deriving_map.{cmi,cmo,cmt}
         ppx src_test/show/test_deriving_show.pp.ml (exit 1)
(cd _build/default && .ppx/4c4b0dc849c26ef889ee6f55cb3a0672/ppx.exe -o src_test/show/test_deriving_show.pp.ml --impl src_test/show/test_deriving_show.ml --dump-ast)
File "test_deriving_show.cppo.ml", line 88, characters 22-23:
Error: Syntax error

Let me know if this is a bad idea somehow! ❤️

[gasche]

This looks very sensible, will merge when CI returns.

The reason why the CI hasn't caught it earlier is that we don't have 4.02 CI anymore. I'm trying to fix this in #205.