ruby-mode.el: puts and printf do not require args

* lisp/progmodes/ruby-mode.el (ruby-font-lock-keywords): puts and
printf can be called without arguments, so the font locking of
"bare" calls to either is incorrect.  The fix is to font-lock them
as for other kernel methods which accepts zero or more arguments
(bug#48180).

lisp/progmodes/ruby-mode.el

@@ -2127,11 +2127,9 @@ It will be properly highlighted even when the call omits parens.")
           "loop"
           "open"
           "p"
-          "print"
           "printf"
           "proc"
           "putc"
-          "puts"
           "require"
           "require_relative"
           "spawn"
@@ -2180,9 +2178,11 @@ It will be properly highlighted even when the call omits parens.")
           "fork"
           "global_variables"
           "local_variables"
+          "print"
           "private"
           "protected"
           "public"
+          "puts"
           "raise"
           "rand"
           "readline"