doc: edit Error.captureStackTrace html comment

Edit to the comment in the stack trace capture, highlighting the use of
the constructorOpt argument in errors.md

Fixes: nodejs#12289
PR-URL: nodejs#12962
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben.bridgewater@fintura.de>

Author: vieiraarturg

doc/api/errors.md

@@ -238,7 +238,7 @@ function MyError() {
 
 // Without passing MyError to captureStackTrace, the MyError
 // frame would show up in the .stack property. By passing
-// the constructor, we omit that frame and all frames above it.
+// the constructor, we omit that frame, and retain all frames below it.
 new MyError().stack;
 ```