doc: fix suspicious heading emphasis in n-api.md

PR-URL: #20086
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Kyle Farnung <kfarnung@microsoft.com>

doc/api/n-api.md

@@ -3475,7 +3475,7 @@ is sufficient and appropriate. Use of the `napi_make_callback` function
 may be required when implementing custom async behavior that does not use
 `napi_create_async_work`.
 
-### *napi_open_callback_scope*
+### napi_open_callback_scope
 <!-- YAML
 added: v9.6.0
 -->
@@ -3500,7 +3500,7 @@ the stack the [`napi_open_callback_scope`][] and
 [`napi_close_callback_scope`][] functions can be used to open/close
 the required scope.
 
-### *napi_close_callback_scope*
+### napi_close_callback_scope
 <!-- YAML
 added: v9.6.0
 -->