Remove SchemaSourceConnector from release artifact

[gharris1727]

Hey, I noticed that this SchemaSourceConnector shows up in the final packaged artifact for multiple connectors. Is this intended to be packaged, or is it a test-only class that users aren't supposed to see?

confluentinc-kafka-connect-sftp-3.1.10                          io.confluent.connect.storage.tools.SchemaSourceConnector
confluentinc-kafka-connect-hdfs2-source-2.5.1                   io.confluent.connect.storage.tools.SchemaSourceConnector
confluentinc-kafka-connect-azure-data-lake-gen1-storage-1.6.15  io.confluent.connect.storage.tools.SchemaSourceConnector
confluentinc-kafka-connect-hdfs-10.2.0                          io.confluent.connect.hdfs.tools.SchemaSourceConnector
confluentinc-kafka-connect-hdfs-10.2.0                          io.confluent.connect.storage.tools.SchemaSourceConnector
confluentinc-kafka-connect-databricks-delta-lake-1.0.9          io.confluent.connect.storage.tools.SchemaSourceConnector
confluentinc-kafka-connect-gcp-dataproc-sink-1.2.2              io.confluent.connect.gcp.dataproc.hdfs.tools.SchemaSourceConnector
confluentinc-kafka-connect-gcp-dataproc-sink-1.2.2              io.confluent.connect.storage.tools.SchemaSourceConnector
confluentinc-kafka-connect-gcs-10.1.4                           io.confluent.connect.storage.tools.SchemaSourceConnector
confluentinc-kafka-connect-hdfs3-source-2.5.1                   io.confluent.connect.storage.tools.SchemaSourceConnector
confluentinc-kafka-connect-s3-10.4.2                            io.confluent.connect.storage.tools.SchemaSourceConnector
confluentinc-kafka-connect-ftps-1.0.4-preview                   io.confluent.connect.storage.tools.SchemaSourceConnector
confluentinc-kafka-connect-hdfs3-1.1.24                         io.confluent.connect.hdfs3.tools.SchemaSourceConnector
confluentinc-kafka-connect-hdfs3-1.1.24                         io.confluent.connect.storage.tools.SchemaSourceConnector
confluentinc-kafka-connect-azure-blob-storage-1.6.15            io.confluent.connect.storage.tools.SchemaSourceConnector
confluentinc-kafka-connect-azure-data-lake-gen2-storage-1.6.15  io.confluent.connect.storage.tools.SchemaSourceConnector