don't depend on greenlet

Author: graingert

pyproject.toml

@@ -75,6 +75,7 @@ legacy_tox_ini = """
     [testenv]
     package = wheel
     wheel_build_env = .pkg
+    deps = httpbin @ https://github.com/graingert/httpbin/archive/refs/heads/patch-1.zip
     extras = test
     commands = pytest -v -s {posargs}
     install_command = python -I -m pip install --use-pep517 {opts} {packages}