Removed delayed approval feature JENKINS-11409

It is a bit too risky to have enabled in large installations
and the dependency feature provides a similar functionality.
Since delayed approval has so far only been in a beta release
we can remove it without much consequence.

Change-Id: I2cf2efc7b1f45be7db3ae69dde6cb8cdc88b405f
[maven-release-plugin] prepare release gerrit-trigger-2.12.0-beta-3
[maven-release-plugin] prepare for next development iteration