Update mysql

Changes:

- https://github.com/docker-library/mysql/commit/a77d4a5: Merge pull request https://github.com/docker-library/mysql/pull/639 from kototoyo/master
- https://github.com/docker-library/mysql/commit/69e4645: modify defaults-file -> defaults-extra-file

library/mysql

@@ -5,13 +5,13 @@ Maintainers: Tianon Gravi <[email protected]> (@tianon),
 GitRepo: https://github.com/docker-library/mysql.git
 
 Tags: 8.0.19, 8.0, 8, latest
-GitCommit: c4d585301408223c27b024ce442b9bcebf0b1855
+GitCommit: 69e4645ced5c687b861ce4a4e8aa3ca4600152b6
 Directory: 8.0
 
 Tags: 5.7.29, 5.7, 5
-GitCommit: c4d585301408223c27b024ce442b9bcebf0b1855
+GitCommit: 69e4645ced5c687b861ce4a4e8aa3ca4600152b6
 Directory: 5.7
 
 Tags: 5.6.47, 5.6
-GitCommit: c4d585301408223c27b024ce442b9bcebf0b1855
+GitCommit: 69e4645ced5c687b861ce4a4e8aa3ca4600152b6
 Directory: 5.6