Remove mentions of RSA-PSK key exchange from documentation

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/ssl_tls12_client.c b/library/ssl_tls12_client.c
index a7f216f..14ce377 100644
--- a/library/ssl_tls12_client.c
+++ b/library/ssl_tls12_client.c
@@ -2137,7 +2137,7 @@
     }
 
     /*
-     * ServerKeyExchange may be skipped with PSK and RSA-PSK when the server
+     * ServerKeyExchange may be skipped with PSK when the server
      * doesn't use a psk_identity_hint
      */
     if (ssl->in_msg[0] != MBEDTLS_SSL_HS_SERVER_KEY_EXCHANGE) {