nixos/tailscale: allow to set `TS_PERMIT_CERT_UID` env variable
nixos/tailscale: allow to set `TS_PERMIT_CERT_UID` env variable

This setting was introduced with Tailscale 1.22.0, see
https://github.com/tailscale/tailscale/releases/tag/v1.22.0

Co-authored-by: pennae <64b2b6d12bfe4baae7dad3d018f8cbf6b0e7a044@quasiparticle.net>

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