doc: add missing n-api version indicator

When the threadsafe functions were promoted to
version 4 from experimental we missed documenting
that. Add the version indicator for these functions
in the doc.

PR-URL: nodejs#27155
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/n-api.md

@@ -4602,6 +4602,7 @@ prevent the event loop from exiting. The APIs `napi_ref_threadsafe_function` and
 
 <!-- YAML
 added: v10.6.0
+napiVersion: 4
 -->
 ```C
 NAPI_EXTERN napi_status
@@ -4645,6 +4646,7 @@ parameters and with `undefined` as its `this` value.
 
 <!-- YAML
 added: v10.6.0
+napiVersion: 4
 -->
 ```C
 NAPI_EXTERN napi_status
@@ -4663,6 +4665,7 @@ This API may be called from any thread which makes use of `func`.
 
 <!-- YAML
 added: v10.6.0
+napiVersion: 4
 -->
 ```C
 NAPI_EXTERN napi_status
@@ -4691,6 +4694,7 @@ This API may be called from any thread which makes use of `func`.
 
 <!-- YAML
 added: v10.6.0
+napiVersion: 4
 -->
 ```C
 NAPI_EXTERN napi_status
@@ -4713,6 +4717,7 @@ This API may be called from any thread which will start making use of `func`.
 
 <!-- YAML
 added: v10.6.0
+napiVersion: 4
 -->
 ```C
 NAPI_EXTERN napi_status
@@ -4741,6 +4746,7 @@ This API may be called from any thread which will stop making use of `func`.
 
 <!-- YAML
 added: v10.6.0
+napiVersion: 4
 -->
 ```C
 NAPI_EXTERN napi_status
@@ -4762,6 +4768,7 @@ This API may only be called from the main thread.
 
 <!-- YAML
 added: v10.6.0
+napiVersion: 4
 -->
 ```C
 NAPI_EXTERN napi_status