Chore(deps-dev): Update pytest requirement from <8 to <9

Updates the requirements on [pytest](https://github.com/pytest-dev/pytest) to permit the latest version.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/main/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@1.0.0b3...8.1.1)

---
updated-dependencies:
- dependency-name: pytest
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

pyproject.toml

@@ -67,7 +67,7 @@ mosquitto = "pytest_mqtt.mosquitto"
 [project.optional-dependencies]
 test = [
   "coverage<8",
-  "pytest<8",
+  "pytest<9",
   "pytest-fixture-order<1",
   "pytest-ordering<1",
 ]