Bump trillian-opensource-ci/db_server in /config/trillian/mysql

Bumps trillian-opensource-ci/db_server from `95cb71a` to `57de589`.

---
updated-dependencies:
- dependency-name: trillian-opensource-ci/db_server
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

config/trillian/mysql/300-mysql-trillian.yaml

@@ -20,7 +20,7 @@ metadata:
     app: mysql-trillian
 spec:
   containers:
-    - image: gcr.io/trillian-opensource-ci/db_server@sha256:95cb71a55b97a95e8b3b646b4a8cb2be63d16c797f7b4a3dd2388dc3e882e3e7
+    - image: gcr.io/trillian-opensource-ci/db_server@sha256:57de5898aba0121104c1865ba4fe2892dfe210e47a693b34556ea10b042b7549
       name: mysql
       env:
         - name: MYSQL_ROOT_PASSWORD