fix(ci): replace healthcheck command

According to MariaDB/mariadb-docker#512 (comment)
the mysqladmin command has been removed from the image.

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>

.github/workflows/e2e-tests.yml

@@ -63,7 +63,7 @@ jobs:
           MYSQL_PASSWORD: hedgedoc
           MYSQL_DATABASE: hedgedoc
           MYSQL_ROOT_PASSWORD: hedgedoc
-        options: --health-cmd "mysqladmin ping" --health-interval 10s --health-timeout 5s --health-retries 10
+        options: --health-cmd "healthcheck.sh --su-mysql --connect --innodb_initialized" --health-interval 10s --health-timeout 5s --health-retries 10
         ports:
           - 3306:3306
     steps: