Remove ignore check for macOS API module now that compatible versions…

… of Python 3.8 are in CI. Ref #547.

conftest.py

@@ -1,21 +1 @@
-import ctypes
-
 collect_ignore = ["hook-keyring.backend.py"]
-
-
-def macos_api_ignore():
-    """
-    Starting with macOS 11, the security API becomes
-    non-viable except on universal2 binaries.
-
-    Ref #525.
-    """
-
-    try:
-        ctypes.CDLL(ctypes.util.find_library('Security')).SecItemAdd
-        return False
-    except Exception:
-        return True
-
-
-collect_ignore.extend(['keyring/backends/macOS/api.py'] * macos_api_ignore())