vision: rename client
vision: rename client

The underlying generated code had a name change.

Change-Id: If8a187307c8e4a32808fdcbae82f145475292a15
Reviewed-on: https://code-review.googlesource.com/8250
Reviewed-by: Sarah Adams <2b342d1c32491b4e7587e4a0e291a5f0f95d4167@google.com>

googleapis/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go,michael-grosshans/google-cloud-go,googleapis/google-cloud-go,michael-grosshans/google-cloud-go