seccomp: remove repeat syscall definitions

Remove redundant syscall definitions in a few Chrome OS policy files
that are causing failures now because of crrev.com/c/2538003.

BUG=chromium:1033137
TEST=None

Change-Id: I176148b04d0a24c42de8e554b64d3d22e3388abd
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/adhd/+/2560570
Tested-by: Nicole Anderson-Au <nvaa@google.com>
Commit-Queue: Jorge Lucangeli Obes <jorgelo@chromium.org>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
2 files changed