vision: remove integration tests
vision: remove integration tests

They are too flaky (often return Internal errors).

Change-Id: I17c8a4aeb8418a94b81e1382a79033cfd684f9f8
Reviewed-on: https://code-review.googlesource.com/13114
Reviewed-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Sarah Adams <2b342d1c32491b4e7587e4a0e291a5f0f95d4167@google.com>

googleapis/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go