chore(deps): update prom/mysqld-exporter docker tag to v0.15.1 #3258

Job	Run time
dockerfile_default (mysql)	10s
dockerfile_default (postgres)	8s
dockerfile_default (mongodb)	17s
dockerfile_ab (ab)	8s
dockerfile_default (rabbitmq)	7s
dockerfile_default (nginx)	9s
dockerfile_default (cassandra)	22s
dockerfile_application (consumer-activemq-quarkus)	16s
dockerfile_postmannewman	8s
dockerfile_monitoring (jenkins)	7s
dockerfile_application (consumer-hazelcast-quarkus)	9s
dockerfile_application (consumer-kafka-quarkus)	12s
dockerfile_application (consumer-rabbitmq-quarkus)	9s
dockerfile_application (consumer-redis-quarkus)	10s
dockerfile_application (converter-kafka-quarkus)	8s
dockerfile_application (converter-rabbitmq-quarkus)	16s
dockerfile_application (jaxrs-activemq-quarkus)	13s
dockerfile_application (jaxrs-cassandra-quarkus)	15s
dockerfile_application (jaxrs-grpc-quarkus)	21s
dockerfile_application (jaxrs-hazelcast-quarkus)	12s
dockerfile_application (jaxrs-kafka-quarkus)	7s
dockerfile_application (jaxrs-memcached-quarkus)	9s
dockerfile_application (jaxrs-mongodb-quarkus)	12s
dockerfile_application (jaxrs-mysql-quarkus)	8s
dockerfile_application (jaxrs-postgres-quarkus)	7s
dockerfile_application (jaxrs-rabbitmq-quarkus)	11s
dockerfile_application (jaxrs-redis-quarkus)	10s
dockerfile_application (producer-kafka-quarkus)	7s
dockerfile_application (randompublish-quarkus)	7s
dockerfile_application (scheduled-quarkus)	9s
dockerfile_application (server-grpc-quarkus)	10s
	5m 34s

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