SHA-1 is allowed for handshake signatures by default

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index a8376a2..0abeb43 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -2269,7 +2269,9 @@
 #if defined(MBEDTLS_KEY_EXCHANGE__WITH_CERT__ENABLED)
 /**
  * \brief          Set the allowed hashes for signatures during the handshake.
- *                 (Default: all SHA2 hashes, largest first.)
+ *                 (Default: all SHA-2 hashes, largest first. Also SHA-1 if
+ *                 the compile-time option
+ *                 `MBEDTLS_TLS_DEFAULT_ALLOW_SHA1_IN_KEY_EXCHANGE` is enabled.)
  *
  * \note           This only affects which hashes are offered and can be used
  *                 for signatures during the handshake. Hashes for message