fix: changes a positional to named arg [(#4092)](GoogleCloudPlatform/…

…python-docs-samples#4092)

[Another PR](GoogleCloudPlatform/python-docs-samples#4041) is blocked due to the use of positional arguments in the Video Intelligence samples. This PR changes one sample to use named arguments.

This fix updates the following region tags:

+ `video_speech_transcription_gcs_beta`

samples/analyze/beta_snippets.py

@@ -62,7 +62,7 @@ def speech_transcription(input_uri):
     )
 
     operation = video_client.annotate_video(
-        input_uri, features=features, video_context=video_context
+        input_uri=input_uri, features=features, video_context=video_context
     )
 
     print("\nProcessing video for speech transcription.")