chore(3p): Bump nixpkgs channels

Bumps both nixos-unstable and nixos-20.03 to today's versions, as per
status.nixos.org

Contains minor fixes to things that broke because of the update:

* tazjin/frog: hardware.u2f is a deprecated setting
* glittershark/system: modSha256 in Go modules is now vendorSha256
* glittershark/owothia: removed version constraint on relude

Change-Id: Ib3e9612b1b06ed547b90e4f8b0ffe5ed7fe0a5c4
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1642
Tested-by: BuildkiteCI
Reviewed-by: glittershark <grfn@gws.fyi>

users/tazjin/nixos/frog/default.nix

@@ -51,7 +51,6 @@ in depot.lib.fix(self: {
   hardware = {
     cpu.amd.updateMicrocode = true;
     enableRedistributableFirmware = true;
-    u2f.enable = true;
     opengl = {
       enable = true;
       driSupport = true;