Update mysql

Changes:

- https://github.com/docker-library/mysql/commit/b7e0196: Merge pull request https://github.com/docker-library/mysql/pull/749 from infosiftr/mysql-user
- https://github.com/docker-library/mysql/commit/6a9edeb: Error early if MYSQL_USER=root to prevent partially initialized databases

library/mysql

@@ -5,16 +5,16 @@ Maintainers: Tianon Gravi <[email protected]> (@tianon),
 GitRepo: https://github.com/docker-library/mysql.git
 
 Tags: 8.0.23, 8.0, 8, latest
-GitCommit: 2966bfbd71cf370770cd880aa45f3c8f155d0aae
+GitCommit: 6a9edebd6ed7b0178b0cce7495bea1777cb9f128
 Directory: 8.0
 File: Dockerfile.debian
 
 Tags: 5.7.33, 5.7, 5
-GitCommit: 2966bfbd71cf370770cd880aa45f3c8f155d0aae
+GitCommit: 6a9edebd6ed7b0178b0cce7495bea1777cb9f128
 Directory: 5.7
 File: Dockerfile.debian
 
 Tags: 5.6.51, 5.6
-GitCommit: 2966bfbd71cf370770cd880aa45f3c8f155d0aae
+GitCommit: 6a9edebd6ed7b0178b0cce7495bea1777cb9f128
 Directory: 5.6
 File: Dockerfile.debian