ocp-index is not compatible with OCaml 5.3 (compiler-libs change)

[kit-ty-kate]

Reported upstream at OCamlPro/ocp-index#171

#=== ERROR while compiling ocp-index.1.3.6 ====================================#
# context              2.3.0~alpha~dev | linux/x86_64 | ocaml-variants.5.3.0+trunk | file:///home/opam/opam-repository
# path                 ~/.opam/5.3/.opam-switch/build/ocp-index.1.3.6
# command              ~/.opam/5.3/bin/dune build -p ocp-index -j 1
# exit-code            1
# env-file             ~/.opam/log/ocp-index-19-048fed.env
# output-file          ~/.opam/log/ocp-index-19-048fed.out
### output ###
# (cd _build/default && /home/opam/.opam/5.3/bin/ocamlc.opt -w -40 -w -9 -g -bin-annot -bin-annot-occurrences -I libs/.indexLib.objs/byte -I /home/opam/.opam/5.3/lib/bytes -I /home/opam/.opam/5.3/lib/ocaml/compiler-libs -I /home/opam/.opam/5.3/lib/ocp-indent/lexer -I /home/opam/.opam/5.3/lib/ocp-indent/utils -intf-suffix .ml -no-alias-deps -o libs/.indexLib.objs/byte/indexOut.cmo -c -impl libs/indexOut.pp.ml)
# File "libs/indexOut.ml", line 124, characters 12-28:
# Error: This expression has type
#          "Outcometree.out_type Format_doc.printer" =
#            "Format_doc.formatter -> Outcometree.out_type -> unit"
#        but an expression was expected of type "Format.formatter -> 'a -> unit"
#        Type "Format_doc.formatter" is not compatible with type "Format.formatter"
# (cd _build/default && /home/opam/.opam/5.3/bin/ocamlc.opt -w -40 -w -9 -g -bin-annot -bin-annot-occurrences -I libs/.indexLib.objs/byte -I /home/opam/.opam/5.3/lib/bytes -I /home/opam/.opam/5.3/lib/ocaml/compiler-libs -I /home/opam/.opam/5.3/lib/ocp-indent/lexer -I /home/opam/.opam/5.3/lib/ocp-indent/utils -intf-suffix .ml -no-alias-deps -o libs/.indexLib.objs/byte/indexBuild.cmo -c -impl libs/indexBuild.pp.ml)
# File "libs/indexBuild.ml", line 166, characters 36-61:
# Error: Unbound value "tree_of_value_description"