Use the client app traffic secret for PHA Finished message

The TLSv1.3 spec requires us to use the client application traffic secret
during generation of the Finished message following a post handshake
authentication.

Fixes #6263

Reviewed-by: Ben Kaduk <kaduk@mit.edu>
(Merged from https://github.com/openssl/openssl/pull/6297)
1 file changed