Update docker.io/bitnami/mysqld-exporter Docker tag to v0.15.1-debian-12-r24

Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

appuio/mariadb-galera/values.yaml

@@ -633,7 +633,7 @@ metrics:
     # -- MariaDB Prometheus exporter image repository
     repository: bitnami/mysqld-exporter
     # -- MariaDB Prometheus exporter image tag (immutable tags are recommended)
-    tag: 0.13.0-debian-10-r75
+    tag: 0.15.1-debian-12-r24
     # -- MariaDB Prometheus exporter image pull policy
     pullPolicy: IfNotPresent
     # -- MariaDB Prometheus exporter image pull secrets.