Bump minor version post VOLTHA2.4 branch out

Change-Id: I4037a00db9723f2ec03672797817e16870a16fb6
diff --git a/VERSION b/VERSION
index 60b9d63..df4a767 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-3.1.23
+3.2.0-dev