dlp: breaking api surface change

[Jean de Klerk]

We just committed the following changes. You'll see them if you run "go get -u", but if you're using dep or another tool to pin to a release version, they won't appear until v0.22.0 is tagged.

We removed the DLP v2beta1 package, since v2 is officially available. Please migrate your code from using the 'v2beta1' package to using the 'v2' package.