pointless_build: remove unused dep_graph field

This has been replaced everywhere by relevant_paths

BUG=chromium:1042283
TEST=regen

Change-Id: I37ce5225ee374bfbb729321dab82d5191ec7b69a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/infra/proto/+/2003422
Reviewed-by: Sean Abraham <seanabraham@chromium.org>
Commit-Queue: Sean Abraham <seanabraham@chromium.org>
Tested-by: Sean Abraham <seanabraham@chromium.org>
3 files changed