Enclose the code that was accidentally a link in "tt"

Author: aycabta

lib/racc/parser.rb

@@ -546,7 +546,7 @@ def yyerror
     end
 
     # Exit parser.
-    # Return value is Symbol_Value_Stack[0].
+    # Return value is +Symbol_Value_Stack[0]+.
     def yyaccept
       throw :racc_jump, 2
     end