docs: pubsub delete topic

[chrishiestand]

In v1beta2, deleting a topic does not delete corresponding subscriptions

"Deletes the topic with the given name. Returns NOT_FOUND if the topic does
not exist. After a topic is deleted, a new topic may be created with the
same name; this is an entirely new topic with none of the old configuration
or subscriptions. Existing subscriptions to this topic are not deleted."

source: https://cloud.google.com/pubsub/reference/rest/v1beta2/projects/topics/delete

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[chrishiestand]

I signed it! (both under my employer and now under my personal github profile)

[googlebot]

CLAs look good, thanks!

[jgeewax]

This is correct (https://cloud.google.com/pubsub/reference/rest/v1beta2/projects/topics/delete)

[jgeewax]

LGTM @stephenplusplus ?

[stephenplusplus]

Thanks @chrishiestand!