Buck: Fix plugin build

Now, that we expose httpclient in the plugin API, we can remove the
hack providing acceptance-framework to the plugin artifact.

And of course it was always wrong to pass wiremock as non-provided
dependency to the plugin. As the consequence this mock library was
shipped in the plugin JAR.

Change-Id: If7ef73f9bea443ddf719cbc6c981255dd93179e3