[DOC] Update description of `Process.daemon` arguments

These arguments can only be `true` or `false` now.  Also add markups.

process.c

@@ -6830,13 +6830,12 @@ static int rb_daemon(int nochdir, int noclose);
  *     Process.daemon()                        -> 0
  *     Process.daemon(nochdir=nil,noclose=nil) -> 0
  *
- *  Detach the process from controlling terminal and run in
- *  the background as system daemon.  Unless the argument
- *  nochdir is true (i.e. non false), it changes the current
- *  working directory to the root ("/"). Unless the argument
- *  noclose is true, daemon() will redirect standard input,
- *  standard output and standard error to null device.
- *  Return zero on success, or raise one of Errno::*.
+ *  Detach the process from controlling terminal and run in the
+ *  background as system daemon.  Unless the argument _nochdir_ is
+ *  +true+, it changes the current working directory to the root
+ *  ("/"). Unless the argument _noclose_ is +true+, daemon() will
+ *  redirect standard input, standard output and standard error to
+ *  null device.  Return zero on success, or raise one of Errno::*.
  */
 
 static VALUE