Limit pytest to <8.0.0 (#945)

Limits [pytest](https://github.com/pytest-dev/pytest) to <8.0.0.
* Pytest 8 breaks when using the asyncio library, see issue
pytest-dev/pytest#11868
* We should use pytest-asyncio instead of the asyncio library directly
once pytest-asyncio supports pytest >=8

---------

Signed-off-by: dependabot[bot] <support@github.com>
Signed-off-by: Elliot Gunton <egunton@bloomberg.net>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Elliot Gunton <egunton@bloomberg.net>

pyproject.toml

@@ -39,7 +39,7 @@ yaml = ["PyYAML"]
 cli = ["cappa", "PyYAML"]
 
 [tool.poetry.group.dev.dependencies]
-pytest = "*"
+pytest = "<8.0.0"
 pytest-cov = "*"
 mypy = "*"
 build = "*"
@@ -128,13 +128,15 @@ source = [
 [tool.ruff]
 line-length = 119
 show-fixes = true
+target-version = "py38"
+src = ["src"]
+
+[tool.ruff.lint]
 select = ["E", "F", "D"]
 ignore = ["E501"]
-target-version = "py38"
 extend-select = ["I"]
-src = ["src"]
 
-[tool.ruff.per-file-ignores]
+[tool.ruff.lint.per-file-ignores]
 "**/__init__.py" = ["F401", "D107"]
 "examples/**" = ["D"]
 "src/hera/events/models/**" = ["D"]
@@ -143,10 +145,10 @@ src = ["src"]
 "tests/**" = ["D"]
 "scripts/graphlib.py" = ["D"]
 
-[tool.ruff.isort]
+[tool.ruff.lint.isort]
 force-wrap-aliases = true
 combine-as-imports = true
 known-first-party = ["hera"]
 
-[tool.ruff.pydocstyle]
+[tool.ruff.lint.pydocstyle]
 convention = "google"