Proto: update cache related constants

The constants cache_sampler_state_cycles and cache_stake_distribution_cycles have not been updated, though they depend on the values of other constants that have been. Note however that adjusting the values is not a safety issue: bigger values would make the cache (so the memory consumption slightly?) larger, while smaller (than ideal) values may degrade a bit the node's performance.

NOTE: the change is made only based on the comments, I have not yet checked if the comment is still valid.