Release v4 of Display Video

[xpressivecode]

https://developers.google.com/display-video/api/deprecations)](https://developers.google.com/display-video/api/deprecations

v4 was released back in March, but we still don't have an updated api client. V3 was sunset Oct 7th.

We're seeing This API version has been sunset. Please migrate to the latest version in the responses.