Fix initial importlib check suite load

Fixes loading initial available checkers via importlib. An invalid
argument had been passed with kwarg `groups` instead of `group`.

compliance_checker/suite.py

@@ -74,7 +74,7 @@ def _get_generator_plugins(cls):
 
         if not hasattr(cls, "suite_generators"):
             gens = importlib_metadata.entry_points(
-                groups="compliance_checker.generators",
+                group="compliance_checker.generators",
             )
             cls.suite_generators = [x.load() for x in gens]