util/syspolicy: remove handler, other dead code

Fixes #17022

Change-Id: I6a0f6488ae3ea75c5844dfcba68e1e8024e930be
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
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Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f