manually add libgoogle-cloud 2.21 migration

.ci_support/migrations/libgoogle_cloud221.yaml

@@ -0,0 +1,46 @@
+__migrator:
+  build_number: 1
+  commit_message: Rebuild for libgoogle_cloud 2.21
+  kind: version
+  migration_number: 1
+google_cloud_cpp:  # legacy setup
+  - '2.21'
+libgoogle_cloud:   # legacy setup
+  - '2.21'
+libgoogle_cloud_devel:
+  - '2.21'
+libgoogle_cloud_all_devel:
+  - '2.21'
+libgoogle_cloud_aiplatform_devel:
+  - '2.21'
+libgoogle_cloud_automl_devel:
+  - '2.21'
+libgoogle_cloud_bigquery_devel:
+  - '2.21'
+libgoogle_cloud_bigtable_devel:
+  - '2.21'
+libgoogle_cloud_compute_devel:
+  - '2.21'
+libgoogle_cloud_dialogflow_cx_devel:
+  - '2.21'
+libgoogle_cloud_dialogflow_es_devel:
+  - '2.21'
+libgoogle_cloud_discoveryengine_devel:
+  - '2.21'
+libgoogle_cloud_dlp_devel:
+  - '2.21'
+libgoogle_cloud_iam_devel:
+  - '2.21'
+libgoogle_cloud_oauth2_devel:
+  - '2.21'
+libgoogle_cloud_policytroubleshooter_devel:
+  - '2.21'
+libgoogle_cloud_pubsub_devel:
+  - '2.21'
+libgoogle_cloud_spanner_devel:
+  - '2.21'
+libgoogle_cloud_speech_devel:
+  - '2.21'
+libgoogle_cloud_storage_devel:
+  - '2.21'
+migrator_ts: 1708358802.0941658