Update revision to 0.51.0 draft

Change-Id: I6adfd59be1799fc004c9051daa409c902bc4bd1d
diff --git a/python/serializer/tosa_serializer.py b/python/serializer/tosa_serializer.py
index e7bcef1..85955aa 100644
--- a/python/serializer/tosa_serializer.py
+++ b/python/serializer/tosa_serializer.py
@@ -30,9 +30,9 @@
 
 # Keep version number in sync with the version default value with schema/tosa.fbs
 TOSA_VERSION_MAJOR = 0
-TOSA_VERSION_MINOR = 50
+TOSA_VERSION_MINOR = 51
 TOSA_VERSION_PATCH = 0
-TOSA_VERSION_DRAFT = False
+TOSA_VERSION_DRAFT = True
 TOSA_VERSION = [
     TOSA_VERSION_MAJOR,
     TOSA_VERSION_MINOR,