gen: rename serviceuser API from Service to APIService
gen: rename serviceuser API from Service to APIService

Change-Id: Ifa65a4a7cdc482b62f5bfe97375bf5470259872e
Reviewed-on: https://code-review.googlesource.com/11171
Reviewed-by: Chris Broadfoot <0c2851a4f8ab4aa5606e69c0757771dd13dbe686@google.com>

googleapis/google-api-go-client,google/google-api-go-client,googleapis/google-api-go-client,google/google-api-go-client