doc: use serial comma in process docs

Refs: nodejs/node#11321
Refs: nodejs/node#17384

PR-URL: nodejs/node#43179
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

doc/api/process.md

@@ -766,7 +766,7 @@ process.on('SIGTERM', handle);
 * `'SIGKILL'` cannot have a listener installed, it will unconditionally
   terminate Node.js on all platforms.
 * `'SIGSTOP'` cannot have a listener installed.
-* `'SIGBUS'`, `'SIGFPE'`, `'SIGSEGV'` and `'SIGILL'`, when not raised
+* `'SIGBUS'`, `'SIGFPE'`, `'SIGSEGV'`, and `'SIGILL'`, when not raised
   artificially using kill(2), inherently leave the process in a state from
   which it is not safe to call JS listeners. Doing so might cause the process
   to stop responding.