VOL-4225 - Bump minor version post voltha-2.8 release tag

Change-Id: Ib698d9ceb766fd0a29a9440168528721ddbfef79
diff --git a/VERSION b/VERSION
index 6aba2b2..50299d1 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-4.2.0
+4.3.0-dev