doc: reference signal(7) for the list of signals

Fixes: https://github.com/nodejs/node/issues/9309
PR-URL: https://github.com/nodejs/node/pull/9323
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>

doc/api/process.md

@@ -374,7 +374,7 @@ The `*-deprecation` command line flags only affect warnings that use the name
 <!--name=SIGINT, SIGHUP, etc.-->
 
 Signal events will be emitted when the Node.js process receives a signal. Please
-refer to sigaction(2) for a listing of standard POSIX signal names such as
+refer to signal(7) for a listing of standard POSIX signal names such as
 `SIGINT`, `SIGHUP`, etc.
 
 The name of each event will be the uppercase common name for the signal (e.g.