Remove unused Ruby client reply helpers

[kpumuk]

This is a follow-up to #3345. I left the old helpers around, so that code generated with the compiler pre- and post- seqid change would work (although pre- would not generate correct sequence IDs nor validate them).

With this cleanup we force people to re-generate, as per Ruby documentation on version upgrade. This will also go into the next release (0.24.0), so I feel like it should not affect anybody.

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