chore(zizmor): drop the local policy copy, the reusable supplies it

netresearch/.github#339 makes the zizmor reusable fetch the organisation policy
at run time when a repo has no .github/zizmor.yml of its own, and removes the
file from the templates. Keeping a copy here would silently win over the shared
policy the next time it really changes, which is how this file came to differ
across the fleet in the first place.

The scan itself is unchanged: the same policy is applied, from one place.

Signed-off-by: Sebastian Mendel <github@sebastianmendel.de>

Author: CybotTM