Leave the preference order for hashes unspecified

We don't seem to have strong feelings about this, so allow ourselves to
change the order later.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index d885d21..b38bd72 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -2943,8 +2943,9 @@
  * \note           By default, all supported hashes whose length is at least
  *                 256 bits are allowed. This is the same set as the default
  *                 for certificate verification
- *                 (#mbedtls_x509_crt_profile_default). Larger hashes are
- *                 preferred.
+ *                 (#mbedtls_x509_crt_profile_default).
+ *                 The preference order is currently unspecified and may
+ *                 change in future versions.
  *
  * \param conf     SSL configuration
  * \param hashes   Ordered list of allowed signature hashes,