use maven_repositories section instead

- buck warning log was suggesting to use [maven_repositories]

Change-Id: Ic3a3e4c7014d294376c60414d8157ed7ccdc07ba
diff --git a/.buckconfig b/.buckconfig
index 283935c..02adf56 100644
--- a/.buckconfig
+++ b/.buckconfig
@@ -13,5 +13,7 @@
     package = //tools/package:onos-package
 
 [download]
-  maven_repo = https://repo1.maven.org/maven2
   in_build = true
+
+[maven_repositories]
+  central = https://repo.maven.apache.org/maven2