nss: PKCS#1 v1.5 signatures can be used for TLS 1.3

A vulnerability exists where it possible to force Network Security Services NSS to sign CertificateVerify with PKCS1 v1.5 signatures when those are the only ones advertised by server in CertificateRequest in TLS 1.3. PKCS1 v1.5 signatures should not be used for TLS 1.3 messages. This vulnerabilit...