dialogflow: Article suggestion feature deprecated

[glasnt]

https://cloud.google.com/agent-assist/docs/deprecations

Article suggestion August 21, 2025

The tests in #10129 are failing for these samples with the error:

[ERROR] com.example.dialogflow.UpdateAnswerRecordTest.testUpdateAnswerRecord  Time elapsed: 0.069 s  <<< ERROR!
com.google.api.gax.rpc.UnimplementedException: io.grpc.StatusRuntimeException: UNIMPLEMENTED: Feature 'ARTICLE_SUGGESTION' is planned for deprecation on April 1, 2026. New setups are not allowed.

These tests should be disabled, but not deleted until the deprecation date.