As of this new major, all milestones should be shipped to central as
well. This commit removes the inclusion of the milestone repository as
this shouldn't be needed anymore.
Closes gh-46420
Create a small Groovy script that can be used in `settings.gradle`
files to extend `repositories` to support the various maven
repositories required for our build.
See gh-42333
Stéphane Nicoll
Phillip Webb