eclass: Remove cargo.eclass

It appears that cargo.eclass is no longer being used, and using it in
the future should be discouraged in favor of the cros-rust.elass
workflow.

BUG=b:338079649
TEST=CQ

Change-Id: I03d4e1aca487ece915120ce35b3bc76d4c5050ef
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/5594232
Auto-Submit: Ryan Beltran <ryanbeltran@chromium.org>
Tested-by: Ryan Beltran <ryanbeltran@chromium.org>
Commit-Queue: Ryan Beltran <ryanbeltran@chromium.org>
Commit-Queue: George Burgess <gbiv@chromium.org>
Reviewed-by: George Burgess <gbiv@chromium.org>
1 file changed