Remove check_line_directives.py

It is no longer needed.

BUG=b:272518464
TEST=CQ

Change-Id: I77b52e0dcf7b8f573b2ab08a0542f663354112e8
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/zephyr/hal_stm32/+/7311959
Tested-by: Jeremy Bettis <jbettis@chromium.org>
Reviewed-by: Jon Murphy <jpmurphy@google.com>
Commit-Queue: Jeremy Bettis <jbettis@chromium.org>