doc: update n-api support matrix

As thread safe functions were back-ported to 8.x and released in 8.16
the documentation should be updated as well.

PR-URL: #27567
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/n-api.md

@@ -148,7 +148,7 @@ available to the module code.
 |       | 1       | 2        | 3        | 4        |
 |:-----:|:-------:|:--------:|:--------:|:--------:|
 | v6.x  |         |          | v6.14.2* |          |
-| v8.x  | v8.0.0* | v8.10.0* | v8.11.2  |          |
+| v8.x  | v8.0.0* | v8.10.0* | v8.11.2  | v8.16.0  |
 | v9.x  | v9.0.0* | v9.3.0*  | v9.11.0* |          |
 | v10.x |         |          | v10.0.0  |          |
 | v11.x |         |          | v11.0.0  | v11.8.0  |