keep default list of signature algorithms as-is; new app should register the certificate verification callback

This reverts commit 983ccf4fc3f43e48bcccd9ba2582aee508d997e1.
diff --git a/lib/picotls.c b/lib/picotls.c
index 0e46152..210d530 100644
--- a/lib/picotls.c
+++ b/lib/picotls.c
@@ -1522,7 +1522,7 @@
 static int push_signature_algorithms(ptls_verify_certificate_t *vc, ptls_buffer_t *sendbuf)
 {
     /* The list sent when verify callback is not registered */
-    static const uint16_t default_algos[] = {PTLS_SIGNATURE_ED25519, PTLS_SIGNATURE_RSA_PSS_RSAE_SHA256, PTLS_SIGNATURE_ECDSA_SECP256R1_SHA256,
+    static const uint16_t default_algos[] = {PTLS_SIGNATURE_RSA_PSS_RSAE_SHA256, PTLS_SIGNATURE_ECDSA_SECP256R1_SHA256,
                                              PTLS_SIGNATURE_RSA_PKCS1_SHA256, PTLS_SIGNATURE_RSA_PKCS1_SHA1, UINT16_MAX};
     int ret;