fix: reduce StreamConnection visibility since it is not supposed to be public. (#2196)

* fix: reduce StreamConnection visiblity since it is not supposed to be a public class

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Author: yirutang

google-cloud-bigquerystorage/clirr-ignored-differences.xml

@@ -169,5 +169,9 @@
     <method>com.google.protobuf.DynamicMessage convertToProtoMessage(com.google.protobuf.Descriptors$Descriptor, com.google.cloud.bigquery.storage.v1.TableSchema, java.lang.Object, boolean)</method>
     <to>com.google.protobuf.DynamicMessage convertToProtoMessage(com.google.protobuf.Descriptors$Descriptor, com.google.cloud.bigquery.storage.v1.TableSchema, java.lang.Iterable, boolean)</to>
   </difference>
+  <difference>
+    <differenceType>1001</differenceType>
+    <className>com/google/cloud/bigquery/storage/v1/StreamConnection</className>
+  </difference>
 </differences>
 

google-cloud-bigquerystorage/src/main/java/com/google/cloud/bigquery/storage/v1/StreamConnection.java

@@ -36,7 +36,7 @@
  *
  * <p>It's user's responsibility to do the flow control and maintain the lifetime of the requests.
  */
-public class StreamConnection {
+class StreamConnection {
   private BidiStreamingCallable<AppendRowsRequest, AppendRowsResponse> bidiStreamingCallable;
   private ClientStream<AppendRowsRequest> clientStream;