Remove some unnecessary function pointers from OSSL_RECORD_METHOD

Remove some unnecessary function pointers from OSSL_RECORD_METHOD

We had some temporary function pointers in OSSL_RECORD_METHOD which were
only necessary during the process of refactoring the read record layer.
These are no longer required so can be removed.

Reviewed-by: Hugo Landau <hlandau@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/18132)