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>

ci-builds.nix

@@ -102,7 +102,9 @@ in lib.fix (self: {
     hgeometry-combinatorial
     vinyl
     comonad-extras
-    depot.third_party.haskell-language-server.ghc883
+
+    # TODO(grfn): Disabled because of build errors with recent nixpkgs
+    # depot.third_party.haskell-language-server.ghc883
   ];
 
   # User-specific build targets
@@ -116,7 +118,7 @@ in lib.fix (self: {
   ];
 
   glittershark = with depot.users.glittershark; [
-    xanthous
+    # xanthous
     keyboard.layout
     owothia