Client library incorrectly returns error when FLAC is used with long-running-recognize

[pbogle]

The client library incorrectly returns an error when anything other than LINEAR16 is used for a long-running recognize request:

https://github.com/GoogleCloudPlatform/google-cloud-python/blob/master/speech/google/cloud/speech/sample.py#L173

The v1 server support all encodings so this breaks functionality.

In general, the client library should almost never do it's own validation; it should always delegate to the server to be sure that that behavior and error messages are consistent across APIs.

[dhermes]

In general, the client library should almost never do it's own validation; it should always delegate to the server to be sure that that behavior and error messages are consistent across APIs.

I am +(a million) on this.