Merge pull request #24650: Remove 'Hidden' attribute from serviceAccount PipelineOption (#24642)

Author: kennknowles

runners/google-cloud-dataflow-java/src/main/java/org/apache/beam/runners/dataflow/options/DataflowPipelineOptions.java

@@ -31,7 +31,6 @@
 import org.apache.beam.sdk.options.Default;
 import org.apache.beam.sdk.options.DefaultValueFactory;
 import org.apache.beam.sdk.options.Description;
-import org.apache.beam.sdk.options.Hidden;
 import org.apache.beam.sdk.options.PipelineOptions;
 import org.apache.beam.sdk.options.StreamingOptions;
 import org.apache.beam.sdk.options.Validation;
@@ -120,7 +119,6 @@ public interface DataflowPipelineOptions
   void setDataflowServiceOptions(List<String> options);
 
   /** Run the job as a specific service account, instead of the default GCE robot. */
-  @Hidden
   @Experimental
   @Description("Run the job as a specific service account, instead of the default GCE robot.")
   String getServiceAccount();