speech: is_final not returning true for stream in German, French, Spanish, but working for English

## In which file did you encounter the issue?
python-docs-samples/speech/microphone/transcribe_streaming_mic.py

## Did you change the file? If so, how?

- add credentials in the beginning

- change language_code to de-DE or fr-FR

- line 174 ff (just print the transcript and the is_final state continue afterwards)

transcript = result.alternatives[0].transcript
print(transcript, result.is_final)
continue

## Describe the issue
in English, the is_final state will turn to true (everything works fine), but does not for German, French or Spanish
the end of sequence is not detected or returned

Please replace *.json by the real json-file-name
[githubSpeechToText.txt](https://github.com/GoogleCloudPlatform/python-docs-samples/files/12570181/githubSpeechToText.txt)