tls-crypto: Fix invalid signature algorithm list building

List building also added an additional length field which is required by
client-side TLS extensions but not for server-side certificate request
extension. Now the method only returns a list of supported signature
algorithms and the implementation is responsible to add additional
length fields.

Fixes: 07f826af67 ("Fixed encoding of TLS extensions (elliptic_curves and signature_algorithms)")

src/libtls/tls_crypto.c

@@ -1474,7 +1474,6 @@ METHOD(tls_crypto_t, get_signature_algorithms, void,
 		}
 	}
 
-	supported->wrap16(supported);
 	writer->write_data16(writer, supported->get_buf(supported));
 	supported->destroy(supported);
 }