Ignore PKCS1 based sig algs in TLSv1.3

In TLSv1.3 we must use PSS based sig algs for RSA signing. Ignore any
shared sig algs which are PKCS1 based.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2157)