[docs] Mention GCS when going over Tiered Storage in docs (#4343)
[docs] Mention GCS when going over Tiered Storage in docs (#4343)

* Mention GCS when going over Tiered Storage

* Minor re-wording

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