transport: remove git_transport_options.push_cert
This field was set in transport_set_option, but never read in the push
code. The push code basically ignores the smart_options field
entirely, and derives its options from the flags arguments to the
push* callbacks. Note that in git_transport_push there are already
several args set from flags that have no corresponding field in
git_transport_options; after this change, push_cert is just like
those.
Signed-off-by: Dave Borowitz <dborowitz@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>