doc: fix napi version for node_api_symbol_for

PR-URL: #42878
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Michael Dawson <[email protected]>

Author: danielleadams

doc/api/n-api.md

@@ -2508,7 +2508,6 @@ of the ECMAScript Language Specification.
 
 <!-- YAML
 added: v16.15.0
-napiVersion: v16.15.0
 -->
 
 > Stability: 1 - Experimental