doc: fix typo in n-api.md

PR-URL: #18590
Reviewed-By: Jon Moss <me@jonathanmoss.me>
Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>

doc/api/n-api.md

@@ -3449,7 +3449,7 @@ invoking the callback. This should be a value previously obtained
 from [`napi_async_init`][].
 - `[out] result`: The newly created scope.
 
-There are cases(for example resolving promises) where it is
+There are cases (for example resolving promises) where it is
 necessary to have the equivalent of the scope associated with a callback
 in place when making certain N-API calls.  If there is no other script on
 the stack the [`napi_open_callback_scope`][] and