wscript: drop unused local VERSION variables

pyflakes correctly points out problems like:
  gtk2_ardour/wscript:537:5 local variable 'VERSION' is assigned to but never used

session_utils/wscript

@@ -67,7 +67,6 @@ def build_ardour_util(bld, util):
         obj.linkflags = ' -lintl'
 
 def build(bld):
-    VERSION = "%s.%s" % (bld.env['MAJOR'], bld.env['MINOR'])
     # session-utils depend on the dummy backend
     if not "dummy" in bld.env['BACKENDS']:
         return