update ocamltop-gtk opam files; require ocaml < 4.03.0

[zoggy]

No description provided.

[dsheets]

{build}?

[yallop]

The build's failing on 4.02:

### stderr ###
# findlib: [WARNING] Interface topdirs.cmi occurs in several directories: /usr/lib/ocaml, /usr/lib/ocaml/compiler-libs
# findlib: [WARNING] Interface topdirs.cmi occurs in several directories: /usr/lib/ocaml, /usr/lib/ocaml/compiler-libs
# findlib: [WARNING] Interface topdirs.cmi occurs in several directories: /usr/lib/ocaml, /usr/lib/ocaml/compiler-libs
# findlib: [WARNING] Interface topdirs.cmi occurs in several directories: /usr/lib/ocaml, /usr/lib/ocaml/compiler-libs
# File "ocamltop.ml", line 93, characters 23-28:
# Error: This pattern matches values of type 'a * 'b
#        but a pattern was expected which matches values of type
#          Parsetree.extension_constructor
# make: *** [ocamltop.cmo] Error 2

[zoggy]

Let's remove this package, since it seems unused and I don't intend to maintain it. Better alternatives exist with utop and ocaml-top.

[camelus]

✅ No new or changed opam files 3118796

[yallop]

Ok; since nothing depends on this package, removing it is unlikely to cause problems.