Merge pull request #22506 from royclarkson

* gh-22506:
  Update conditional inclusion of milestone repository

Closes gh-22506

build.gradle

@@ -17,7 +17,7 @@ allprojects {
 
 	repositories {
 		mavenCentral()
-		if (!version.endsWith('RELEASE')) {
+		if (version.contains('-')) {
 			maven { url "https://repo.spring.io/milestone" }
 		}
 		if (version.endsWith('-SNAPSHOT')) {