[doc][monitoring] Fix doc issue about pulsar_storage_backlog_size metric
[doc][monitoring] Fix doc issue about pulsar_storage_backlog_size metric


yahoo/pulsar,yahoo/pulsar,massakam/pulsar,massakam/pulsar,yahoo/pulsar,massakam/pulsar,merlimat/pulsar,merlimat/pulsar,yahoo/pulsar,massakam/pulsar,merlimat/pulsar,massakam/pulsar,yahoo/pulsar,merlimat/pulsar,massakam/pulsar,merlimat/pulsar,merlimat/pulsar,yahoo/pulsar