Tidy up imports in test_ptrace.rs
Tidy up imports in test_ptrace.rs

MarkusJais/nix-rust,Susurrus/nix,nix-rust/nix,asomers/nix,geofft/nix-rust,asomers/nix,nix-rust/nix,berkowski/nix,berkowski/nix,geofft/nix-rust,carllerche/nix-rust,MarkusJais/nix-rust,xd009642/nix,berkowski/nix,carllerche/nix-rust,xd009642/nix,carllerche/nix-rust,xd009642/nix,Susurrus/nix,geofft/nix-rust,MarkusJais/nix-rust,Susurrus/nix