chore(Poetry): Group dev deps with updated syntax

Previously, development dependencies were grouped under
[tool.poetry.dev-dependencies] in pyproject.toml. This syntax will soon
be deprecated. Group development dependencies under
[tool.poetry.group.dev.dependencies], the updated syntax as of Poetry
v1.2.0.

Author: mwarres

poetry.lock

@@ -19,6 +19,6 @@ build-backend = "poetry.core.masonry.api"
   # Keep in sync with .pre-commit-config.yaml and .tool-versions.
   python = "==3.11.5"
 
-  [tool.poetry.dev-dependencies]
+  [tool.poetry.group.dev.dependencies]
   commitizen = "==3.8.2" # Keep in sync with .pre-commit-config.yaml.
   pre-commit = "==3.4.0"