Use repo.spring.io/release for plugin repository

Issue gh-578

settings.gradle

@@ -1,7 +1,7 @@
 pluginManagement {
 	repositories {
 		gradlePluginPortal()
-		maven { url 'https://repo.spring.io/plugins-release' }
+		maven { url 'https://repo.spring.io/release' }
 	}
 }