Ntp default restrictions

[reardencode]

Motivation for this change

#50732

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Fits CONTRIBUTING.md.

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[reardencode]

sorry about that initial push - failed to push rebase onto master.

[Mic92]

In https://github.com/NixOS/nixpkgs/blob/master/nixos/doc/manual/release-notes/rl-1903.xml we should mention the new defaults. Some people maybe rely on them.