doc: update Node-api version matrix

- add 14.x version in which Node-api version 8
  was added.

Signed-off-by: Michael Dawson <mdawson@devrus.com>

PR-URL: #39197
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>

doc/api/n-api.md

@@ -326,7 +326,7 @@ listed as supporting a later version.
     <td>v14.0.0</td>
     <td>v14.0.0</td>
     <td>v14.12.0</td>
-    <td></td>
+    <td>v14.17.0</td>
   </tr>
   <tr>
     <th scope="row">v15.x</th>