Update flake inputs

flake.lock

@@ -2,11 +2,11 @@
   "nodes": {
     "emacs-overlay": {
       "locked": {
-        "lastModified": 1636622352,
-        "narHash": "sha256-HZkdAcDh1jS+19vy72oYR1qymh0hrxccBbdskHPt95c=",
+        "lastModified": 1638873958,
+        "narHash": "sha256-mXixK5YP9EwMaVRxXNdnbL6VGTtBrLMPb0+41tfAfro=",
         "owner": "nix-community",
         "repo": "emacs-overlay",
-        "rev": "80db8e4e9f25e81662a244a96029f3427fe3d5b9",
+        "rev": "555de7d00eb7c8df21242fdad6f3a6f2201e7e14",
         "type": "github"
       },
       "original": {
@@ -17,11 +17,11 @@
     },
     "flake-utils": {
       "locked": {
-        "lastModified": 1634851050,
-        "narHash": "sha256-N83GlSGPJJdcqhUxSCS/WwW5pksYf3VP1M13cDRTSVA=",
+        "lastModified": 1638122382,
+        "narHash": "sha256-sQzZzAbvKEqN9s0bzWuYmRaA03v40gaJ4+iL1LXjaeI=",
         "owner": "numtide",
         "repo": "flake-utils",
-        "rev": "c91f3de5adaf1de973b797ef7485e441a65b8935",
+        "rev": "74f7e4319258e287b0f9cb95426c9853b282730b",
         "type": "github"
       },
       "original": {
@@ -32,16 +32,18 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1636650511,
-        "narHash": "sha256-dZLCKpliQCl8xDFyQDXUD/EjOh3W3H5Jj1PZ3+INWaY=",
+        "lastModified": 1638535497,
+        "narHash": "sha256-tk5LNbdkUhALp00+r5ZmQ3t7n2d5M7YUQB+MznWvVOg=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "68a6a4e276e26019b090bb587a8d7b26c4f92532",
+        "rev": "c71f061c68ba8ce53471b767d5049cbd0f3d8490",
         "type": "github"
       },
       "original": {
-        "id": "nixpkgs",
-        "type": "indirect"
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
       }
     },
     "root": {