Stop relying on repo.spring.io/milestone

As of this generation, all milestones are to be released on Maven
Central. This commit makes sure we no longer rely on our own milestone
repository to catch that something we depend on was not released
properly.

Closes gh-1664

Author: snicoll

gradle/plugins/conventions-plugin/src/main/java/org/springframework/ws/gradle/conventions/JavaBasePluginConventions.java

@@ -29,8 +29,6 @@
  */
 class JavaBasePluginConventions {
 
-	static final String SPRING_MILESTONE_REPOSITORY_NAME = "Spring Milestones";
-
 	static final String SPRING_SNAPSHOT_REPOSITORY_NAME = "Spring Snapshots";
 
 	static final String SHIBBOLETH_RELEASES_REPOSITORY_NAME = "Shibboleth Releases";
@@ -58,12 +56,6 @@ private void configureRepositories(Project project) {
 			});
 		});
 		String version = project.getVersion().toString();
-		if (version.contains("-")) {
-			project.getRepositories().maven((repository) -> {
-				repository.setName(SPRING_MILESTONE_REPOSITORY_NAME);
-				repository.setUrl("https://repo.spring.io/milestone");
-			});
-		}
 		if (version.endsWith("-SNAPSHOT")) {
 			project.getRepositories().maven((repository) -> {
 				repository.setName(SPRING_SNAPSHOT_REPOSITORY_NAME);