fix(10685): display hint when no action field in rule · ocaml/dune@f18b834

Canceling since a higher priority waiting request for 'CI @ maiste:fix/10685-alias' exists

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Unexpected input(s) 'opam-depext', valid inputs are ['allow-prerelease-opam', 'ocaml-compiler', 'opam-repositories', 'opam-pin', 'opam-local-packages', 'opam-disable-sandboxing', 'dune-cache', 'cache-prefix', 'github-token']