Deps: install sapling parameters files via opam

Context

Depends on opam-repository!413 (merged)

On our journey to replace tezos/opam-repository by a opam lock files there were the install of sapling paramter files. This MR removes this obstacle.

Manually testing the MR

• rm _opam
• make build-dev-deps && eval $(opam env) && make
• src/bin_node/octez-sandboxed-node.sh 4 (shouldn't complain about missing sapling parameter files...)

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR