doc: add --update-assert-snapshot to node.1

PR-URL: #44429
Reviewed-By: Moshe Atlow <moshe@atlow.co.il>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>

doc/node.1

@@ -483,6 +483,9 @@ Track heap object allocations for heap snapshots.
 .It Fl -unhandled-rejections=mode
 Define the behavior for unhandled rejections. Can be one of `strict` (raise an error), `warn` (enforce warnings) or `none` (silence warnings).
 .
+.It Fl -update-assert-snapshot
+Updates snapshot files used by `assert.snapshot()`.
+.
 .It Fl -use-bundled-ca , Fl -use-openssl-ca
 Use bundled Mozilla CA store as supplied by current Node.js version or use OpenSSL's default CA store.
 The default store is selectable at build-time.