Fix `@AutoService` example to reflect the fact that javax.annotation.processing.Processor is an interface, not a class.
Fix `@AutoService` example to reflect the fact that javax.annotation.processing.Processor is an interface, not a class.

Closes https://github.com/google/auto/pull/495

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=157161342

google/auto,eamonnmcmanus/auto,google/auto,MaTriXy/auto,MaTriXy/auto,eamonnmcmanus/auto,eamonnmcmanus/auto,google/auto