Update flake.nix for v0.22.1 (#186)

Updates flake.nix version to 0.22.1 for the v0.22.1 release.

Author: wesm

flake.nix

@@ -15,7 +15,7 @@
         packages = {
           default = pkgs.buildGoModule {
             pname = "roborev";
-            version = "0.22.0";
+            version = "0.22.1";
 
             src = ./.;