Remove stable from help wording (There will be only one main branch for now)

youtube-dl

@@ -3159,7 +3159,7 @@ def parseOpts():
 	general.add_option('-v', '--version',
 			action='version', help='print program version and exit')
 	general.add_option('-U', '--update',
-			action='store_true', dest='update_self', help='update this program to latest stable version')
+			action='store_true', dest='update_self', help='update this program to latest version')
 	general.add_option('-i', '--ignore-errors',
 			action='store_true', dest='ignoreerrors', help='continue on download errors', default=False)
 	general.add_option('-r', '--rate-limit',