doc: close backtick in process.title description

PR-URL: https://github.com/nodejs/node/pull/4534
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Michaël Zasso <mic.besace@gmail.com>

doc/api/process.markdown

@@ -891,7 +891,7 @@ See [the tty docs][] for more information.
 
 ## process.title
 
-Getter/setter to set what is displayed in `ps.
+Getter/setter to set what is displayed in `ps`.
 
 When used as a setter, the maximum length is platform-specific and probably
 short.