Remove a now internal type from Declarations. #3080

Job	Run time
Web Worker Build	12m 48s
Opam dev install	10m 39s
Nix (ubuntu-latest)	1m 36s
Nix (macOS-latest)	3m 29s
build (ubuntu-latest, 4.14.x, default: https://github.com/ocaml/opam-repository.git)	10m 52s
build (ubuntu-latest, 4.13.x, default: https://github.com/ocaml/opam-repository.git)	10m 16s
client-compile	13s
Nix Flake Check	55s
build (ubuntu-latest, 4.12.x, default: https://github.com/ocaml/opam-repository.git)	10m 51s
build (ubuntu-latest, 5.0.x, default: https://github.com/ocaml/opam-repository.git)	11m 27s
build (ubuntu-latest, 5.1.x, default: https://github.com/ocaml/opam-repository.git)	10m 57s
build (ubuntu-latest, 5.2.x, default: https://github.com/ocaml/opam-repository.git)	11m 9s
build (macos-latest, 4.14.x, default: https://github.com/ocaml/opam-repository.git)	10m 22s
build (Windows Latest, 4.14, windows-latest, windows-5.0: https://github.com/dra27/opam-repositor...	14m 36s
	2h 0m 10s

Provide feedback