Proto: Drop smart rollups’ origination proofs

Context

Following !8815 (merged), it becomes trivial to remove the need for an origination proof in the origination operation. This MR tackles this by simply removing the argument of the operation (and the companion RPC).

We might want to adopt a more gentle approach where both the argument and the RPC are deprecated, but it’s not clear to me. Looks like the rest of the ecosystem is okay with us moving forward directly, so… I guess this MR is ready.

Manually testing the MR

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.
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