systemd: Remove cx7 martian logging mitigation

We can no longer reproduce the race condition with martian logs, so we
should remove the mitigation that disables them. See b/425951022 for
more details.

BUG=b/428054225,b/425951022
TEST=presubmit
RELEASE_NOTE=None

Change-Id: I2b0a940f05663b1db63003e365d0eae1a8349836
Reviewed-on: https://cos-review.googlesource.com/c/cos/overlays/board-overlays/+/105779
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Miri Amarilio <mirilio@google.com>
3 files changed