Remove OpenSSLEngine.getSecretKeyById.

This codepath was never completed and has since been superceded by the
AndrodKeyStore work and not useful for Conscrypt since all HMAC keys in
TLS are derived from the key exchange.

(cherry picked from commit 922aa71c87925dade1f27d3cd1388324d24b852d)

Change-Id: Id8dd7cd63f19ee8f2c07edbfcb503c568da45f92
3 files changed