shell.nix: Bump poetry2nix to the most recent version

The new `poetry2nix` version includes overrides which are required for
recent versions of some Python packages (in particular, `jsonschema` and
`dotty-dict`).

util/nix/sources.json

@@ -29,10 +29,10 @@
         "homepage": "",
         "owner": "nix-community",
         "repo": "poetry2nix",
-        "rev": "88ffae91c605aaafc2797f4096ca9f065152796a",
-        "sha256": "0iq9jlzz92r3ax1ymg00cn4s8c1wi3jgh1693abyyn0baq7gixrb",
+        "rev": "11c0df8e348c0f169cd73a2e3d63f65c92baf666",
+        "sha256": "0i3wbp2p0x6bpj07sqpvkbx4lvjm0irvpmv2bjqx8k02mpjm7dg2",
         "type": "tarball",
-        "url": "https://github.com/nix-community/poetry2nix/archive/88ffae91c605aaafc2797f4096ca9f065152796a.tar.gz",
+        "url": "https://github.com/nix-community/poetry2nix/archive/11c0df8e348c0f169cd73a2e3d63f65c92baf666.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     }
 }