test: remove migrated repositories from downstream unit tests (googleapis#4125)

Author: chingor13

.github/workflows/downstream.yaml

@@ -18,11 +18,7 @@ jobs:
           - google-cloud-java
           - java-bigtable
           - java-bigquery
-          - java-bigquerystorage
-          - java-datastore
           - java-firestore
-          - java-logging
-          - java-logging-logback
           - java-pubsub
           - java-pubsublite
           - java-spanner-jdbc