Update include/mbedtls/ssl_internal.h

Mention where an internal function is defined instead of just saying that it's internal.

Co-Authored-By: Gilles Peskine <gilles.peskine@arm.com>
diff --git a/include/mbedtls/ssl_internal.h b/include/mbedtls/ssl_internal.h
index c8d6d10..74c709c 100644
--- a/include/mbedtls/ssl_internal.h
+++ b/include/mbedtls/ssl_internal.h
@@ -1734,7 +1734,7 @@
  * later delivery.
  *
  * The check for pending alerts must be done by calling
- * the (static internal) function ssl_send_pending_fatal_alert().
+ * the function ssl_send_pending_fatal_alert() in ssl_tls.c.
  * Currently, it happens only during the handshake loop.
  *
  * This function must not be called multiple times without