tools: correct usage message for genv8constants.py

PR-URL: #36606
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

tools/genv8constants.py

@@ -14,7 +14,7 @@
 import errno
 
 if len(sys.argv) != 3:
-  print("usage: objsym.py outfile libv8_base.a")
+  print("Usage: genv8constants.py outfile libv8_base.a")
   sys.exit(2)
 
 outfile = open(sys.argv[1], 'w')