Migrate to the latest `io.spring.develocity.conventions` plugin

[artembilan]

Something like this is enough from now on:

plugins {
	id 'io.spring.develocity.conventions' version '0.0.21'
}

In other words we don't need to manage com.gradle.develocity plugin any more. It comes transitively from the mentioned convensions.

More info is here: https://github.com/spring-io/develocity-conventions/issues/92

[onobc]

This was on my todo list but now it is an official issue - thank you.