StandaloneSiteTest: Remove extra lines in execute

Remove superfluous lines wrongfully kept by I5c1a23713 merge resolution.

Change-Id: I67b6925ee23a6220f5f77b87fdb862906aaa35bf

java/com/google/gerrit/acceptance/StandaloneSiteTest.java

@@ -206,8 +206,6 @@ public abstract class StandaloneSiteTest {
 
   protected static String execute(
       ImmutableList<String> cmd, File dir, ImmutableMap<String, String> env) throws IOException {
-    ProcessBuilder pb = new ProcessBuilder(cmd);
-    pb.directory(dir).redirectErrorStream(true);
     return execute(cmd, dir, env, null);
   }