pyprojecy.toml: use new group syntax

poetry wants us to use `poetry add --group=dev` now, which generates
this syntax in the toml.

Author: alanorth

pyproject.toml

@@ -13,14 +13,12 @@ psycopg2 = "^2.9.1"
 requests = "^2.24.0"
 falcon-swagger-ui = {git = "https://github.com/alanorth/falcon-swagger-ui.git", rev="falcon3-update-swagger-ui"}
 
-[tool.poetry.dev-dependencies]
-flake8 = "^6.0.0"
-pytest = "^7.0.0"
-black = "^23.0.0"
-isort = "^5.9.1"
-
 [tool.poetry.group.dev.dependencies]
+black = "^23.0.0"
 fixit = "^2.1.0"
+flake8 = "^6.0.0"
+isort = "^5.9.1"
+pytest = "^7.0.0"
 
 [build-system]
 requires = ["poetry>=0.12"]