doc: fix syntax in N-API documentation

PR-URL: https://github.com/nodejs/node/pull/31466
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Bryan English <bryan@bryanenglish.com>
Reviewed-By: Gabriel Schulhof <gabriel.schulhof@intel.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>

doc/api/n-api.md

@@ -1436,7 +1436,7 @@ napiVersion: 1
 ```C
 NAPI_EXTERN napi_status napi_reference_unref(napi_env env,
                                              napi_ref ref,
-                                             uint32_t* result););
+                                             uint32_t* result);
 ```
 
 * `[in] env`: The environment that the API is invoked under.