Temporarily add SNAPSHOT plugin repository

This is required as otherwise they're deactivated during the staging of
a release. We should reconsider our dependency on Spring Boot SNAPSHOTs
in our samples.

Author: bclozel

settings.gradle

@@ -5,8 +5,8 @@ pluginManagement {
 		maven {
 			url 'https://repo.spring.io/release'
 		}
-		if (version.endsWith('-SNAPSHOT')) {
-			maven { url "https://repo.spring.io/snapshot" }
+		maven {
+			url "https://repo.spring.io/snapshot"
 		}
 	}
     resolutionStrategy {