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>