crosvm: drop code for running integration tests

These are no longer by default as they have been extracted into their
own crate, so this code wasn't doing anything.  If we did want to run
the integration tests again, we'd have to download kernel and rootfs
binaries from Google, and that's more trouble than it's worth.

pkgs/applications/virtualization/crosvm/default.nix

@@ -1,7 +1,6 @@
 { stdenv, lib, rustPlatform, fetchgit
 , minijail-tools, pkg-config, wayland-scanner
 , libcap, libdrm, libepoxy, minijail, virglrenderer, wayland, wayland-protocols
-, linux
 }:
 
 let
@@ -52,10 +51,6 @@ rustPlatform.buildRustPackage rec {
     cp -v seccomp/$arch/*.bpf $out/share/policy/
   '';
 
-  CROSVM_CARGO_TEST_KERNEL_BINARY =
-    lib.optionalString (stdenv.buildPlatform == stdenv.hostPlatform)
-      "${linux}/${stdenv.hostPlatform.linux-kernel.target}";
-
   passthru.updateScript = ./update.py;
 
   meta = with lib; {