misguiding docs: GCP DELTA metrics are exported as Histogram

Hello,

In stackdriver_exporter documentation specified that GCP metric of type DELTA is exported as Gauge, but it is not true.
I encountered a case where it was exported as Histogram.

# HELP stackdriver_bigtable_table_bigtable_googleapis_com_server_latencies Distribution of server request latencies for a table, measured when calls reach Cloud Bigtable.
# TYPE stackdriver_bigtable_table_bigtable_googleapis_com_server_latencies histogram
stackdriver_bigtable_table_bigtable_googleapis_com_server_latencies_bucket{app_profile="default",cluster="NONE",instance="NONE",method="Bigtable.MutateRow",project_id="NONE",table="NONE",unit="ms",zone="us-central1-a",le="0"} 0
stackdriver_bigtable_table_bigtable_googleapis_com_server_request_count{app_profile="default",cluster="NONE",instance="NONE",method="Bigtable.MutateRow",project_id="NONE",table="NONE",unit="1",zone="us-central1-a"} 6

Here is a GCP doc.
I suggest to update the documentation or fix a bug in case export to Histogram was unintended by exporter logic.

Compare the documentation statement about GCP DELTA metrics with the linked Google Cloud metric documentation and the reported Bigtable output. Trace the exporter behavior for the cited metric, then either align the documentation with the observed Histogram output or establish that the exporter behavior should change; done means the discrepancy and intended behavior are resolved.