Add poetry2nix override for jsonschema >= 4.6.0

The `jsonschema` module switched the packaging system to Hatch since
version 4.6.0 (python-jsonschema/jsonschema#957).  The build process for
`jsonschema` now requires the `hatchling` and `hatch-vcs` modules, which
were made available to poetry2nix by the previous commits; add these
modules to `nativeBuildInput` to fix the build.

shell.nix

@@ -29,6 +29,17 @@ let
   pythonEnv = poetry2nix.mkPoetryEnv {
     projectDir = ./nix;
     overrides = poetry2nix.overrides.withDefaults (self: super: {
+      jsonschema =
+        if lib.versionAtLeast super.jsonschema.version "4.6.0"
+        then
+          super.jsonschema.overridePythonAttrs
+            (old: {
+              nativeBuildInputs = (old.nativeBuildInputs or [ ]) ++ [
+                self.hatchling
+                self.hatch-vcs
+              ];
+            })
+        else super.jsonschema;
       pillow = super.pillow.overridePythonAttrs(old: {
         # Use preConfigure from nixpkgs to fix library detection issues and
         # impurities which can break the build process; this also requires