Move update_version.sh to contrib/

Change-Id: I26218cd512a739fc26ba04be05f01260152d785f
diff --git a/Makefile b/Makefile
index 38ff6c8..558f739 100644
--- a/Makefile
+++ b/Makefile
@@ -6,7 +6,7 @@
 	./contrib/check_dependencies.py
 
 version:
-	./update_version.sh
+	./contrib/update_version.sh
 
 manual:
 	$(MAKE) -C doc/manuals