This release introduces only a Tendermint dependency update to v0.34.19 which itself includes two bug fixes related to consensus. See the full changelog from v0.34.17-v0.34.19 here.
See the Cosmos SDK v0.44.8 Changelog for the exhaustive list of all changes.
Full Changelog: https://github.com/cosmos/cosmos-sdk/compare/v0.44.7...v0.44.8