Consistentely apply Spring Data BOM across Spring Session modules

Fixes gh-709

spring-session-data-mongo/build.gradle

@@ -6,11 +6,6 @@ apply plugin: 'spring-io'
 
 description = "Aggregator for Spring Session and Spring Data Mongo"
 
-dependencies {
-	compile project(':spring-session'),
-			"org.springframework.data:spring-data-mongodb:$springDataMongoVersion"
-}
-
 dependencyManagement {
 	springIoTestRuntime {
 		imports {
@@ -18,3 +13,8 @@ dependencyManagement {
 		}
 	}
 }
+
+dependencies {
+	compile project(':spring-session'),
+			"org.springframework.data:spring-data-mongodb:$springDataMongoDBVersion"
+}