v0.14.0-rc2

This release candidate reverts the pruning functionality introduced with IAVL 0.13 due to multiple problems with data corruption, performance, and memory usage. Users are urged to wait for the final 0.14.0 release, and to read the changelog before upgrading.

https://github.com/cosmos/iavl/blob/7bc2ca0310db02a1a0cc49d05988ed97e90fae05/CHANGELOG.md#0140-rc2-june-26-2020