docs: corrects release badge and link (#36)

* docs: corrects release badge and link

* fix: fixes undefined 'beta' substitution

Author: danoscarmike

README.rst

@@ -1,7 +1,7 @@
 Python Client for Google Cloud Video Intelligence
 =================================================
 
-|beta| |pypi| |versions| 
+|ga| |pypi| |versions| 
 
 `Google Cloud Video Intelligence`_ API makes videos searchable, and
 discoverable, by extracting metadata with an easy to use API.
@@ -15,8 +15,8 @@ relevant information at the video, shot or per frame.
 - `Client Library Documentation`_
 - `Product Documentation`_
 
-.. |beta| image:: https://img.shields.io/badge/support-beta-silver.svg
-   :target: https://github.com/googleapis/google-cloud-python/blob/master/README.rst#beta-support
+.. |ga| image:: https://img.shields.io/badge/support-ga-gold.svg
+   :target: https://github.com/googleapis/google-cloud-python/blob/master/README.rst#ga-support
 .. |pypi| image:: https://img.shields.io/pypi/v/google-cloud-videointelligence.svg
    :target: https://pypi.org/project/google-cloud-videointelligence/
 .. |versions| image:: https://img.shields.io/pypi/pyversions/google-cloud-videointelligence.svg