TST: Use hatchling as build backend for test project (#92)

* As the test project does not need any part of setuptools specific
  infrastructure, use hatchling as the build backend.

Author: matthewfeickert

tests/test_package/pyproject.toml

@@ -1,6 +1,6 @@
 [build-system]
-requires = ["setuptools>=61.0"]
-build-backend = "setuptools.build_meta"
+requires = ["hatchling"]
+build-backend = "hatchling.build"
 
 [project]
 name = "test-package"