Fix commented out function declaration

Signed-off-by: Max Fillinger <maximilian.fillinger@foxcrypto.com>
diff --git a/library/ssl_tls13_keys.h b/library/ssl_tls13_keys.h
index 41604c7..07b970a 100644
--- a/library/ssl_tls13_keys.h
+++ b/library/ssl_tls13_keys.h
@@ -656,6 +656,7 @@
  * \param[in]   label_len  The length of label.
  * \param[out]  out  The output buffer for the exported key. Must have room for at least out_len bytes.
  * \param[in]   out_len  Length of the key to generate.
+ */
 int mbedtls_ssl_tls13_exporter(psa_algorithm_t hash_alg,
                                const unsigned char *secret, size_t secret_len,
                                const unsigned char *label, size_t label_len,