commit-graph: drop redundant call to "lite" verification

commit-graph: drop redundant call to "lite" verification

The idea of verify_commit_graph_lite() is to have cheap verification
checks both for everyday use of the graph files (to avoid out of bounds
reads, etc) as well as for doing a full check via "commit-graph verify"
(which will also check the hash, etc).

But the expensive verification checks operate on a commit_graph struct,
which we get by using the normal everyday-reader code! So any problem
we'd find by calling it would have been found before we even got to the
verify_one_commit_graph() function.

Removing it simplifies the code a bit, but also frees us up to move the
"lite" verification steps around within that everyday-reader code.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>