nixos/tests: Revert setting min_free_kbytes

This reverts commit 02b568414d.

With a5bc11f and 6353f58 in place, we really don't need this anymore.

After running about 500 VM tests on my Hydra, it still didn't improve
very much.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>

nixos/modules/testing/test-instrumentation.nix

@@ -88,10 +88,6 @@ let kernel = config.boot.kernelPackages.kernel; in
 
     boot.consoleLogLevel = 7;
 
-    # Make sure we don't hit page allocation failures if the VM's memory is
-    # heavily fragmented.
-    boot.kernel.sysctl."vm.min_free_kbytes" = 16384;
-
     # Prevent tests from accessing the Internet.
     networking.defaultGateway = mkOverride 150 "";
     networking.nameservers = mkOverride 150 [ ];