Update a default value to parameter (GoogleCloudPlatform#1522)

Author: munkhuushmgl

speech/cloud-client/src/main/java/com/example/speech/InfiniteStreamRecognize.java

@@ -176,7 +176,7 @@ public void onError(Throwable t) {
       RecognitionConfig recognitionConfig =
           RecognitionConfig.newBuilder()
               .setEncoding(RecognitionConfig.AudioEncoding.LINEAR16)
-              .setLanguageCode("en-US")
+              .setLanguageCode(languageCode)
               .setSampleRateHertz(16000)
               .build();