lib: use existing isWindows variable

PR-URL: nodejs#48134
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Moshe Atlow <moshe@atlow.co.il>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Mestery <mestery@protonmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>

lib/internal/errors.js

@@ -781,7 +781,7 @@ const fatalExceptionStackEnhancers = {
     // However, fatal error are handled differently and we cannot easily
     // highlight them. On Windows, detecting whether a console supports
     // ANSI escape sequences is not reliable.
-    if (process.platform === 'win32') {
+    if (isWindows) {
       const info = internalBinding('os').getOSInformation();
       const ver = ArrayPrototypeMap(StringPrototypeSplit(info[2], '.'),
                                     Number);