Update mysql

Changes:

- https://github.com/docker-library/mysql/commit/51f9523: Update to 5.7.27-1debian9
- https://github.com/docker-library/mysql/commit/4af273a: Update to 8.0.17-1debian9
- https://github.com/docker-library/mysql/commit/ed0e47e: Update to 5.6.45-1debian9
- https://github.com/docker-library/mysql/commit/079f14e: Update generated README

library/mysql

@@ -4,14 +4,14 @@ Maintainers: Tianon Gravi <[email protected]> (@tianon),
              Joseph Ferguson <[email protected]> (@yosifkit)
 GitRepo: https://github.com/docker-library/mysql.git
 
-Tags: 8.0.16, 8.0, 8, latest
-GitCommit: 3362baccb4352bcf0022014f67c1ec7e6808b8c5
+Tags: 8.0.17, 8.0, 8, latest
+GitCommit: 4af273a07854d7e4b68c5148b8e23b86aa8706e2
 Directory: 8.0
 
-Tags: 5.7.26, 5.7, 5
-GitCommit: 26380f33a0fcd07dda35e37516eb24eaf962845c
+Tags: 5.7.27, 5.7, 5
+GitCommit: 51f9523ad07abacbce90c43eb27390c1c1f76266
 Directory: 5.7
 
-Tags: 5.6.44, 5.6
-GitCommit: 38510a26f56f429817da7cabf5c772756faa5e55
+Tags: 5.6.45, 5.6
+GitCommit: ed0e47e48b8ca3dbc4d68d68f56384bdd1fb5cdb
 Directory: 5.6