databases/redis: Update to 8.0.0

• Update license information. Since 8.0 redis is distributed under triple license of (a) the Redis Source Available License v2 (RSALv2) or (b) the Server Side Public License v1 (SSPLv1) or (c) the GNU Affero General Public License v3 (AGPLv3).
• Add entry to UPDATING.

ChangeLog: https://github.com/redis/redis/releases/tag/8.0.0