Make more linters not fight with each other.

pyright seems confused here, this should be fine without
the staticmethod (but *with* an argument), which pyright
made me remove, of course breaking the test...

Time's up on figuring out why though.

Author: Julian

referencing/_attrs.py

@@ -24,6 +24,7 @@ class UnsupportedSubclassing(Exception):
     pass
 
 
+@staticmethod
 def _do_not_subclass() -> NoReturn:  # pragma: no cover
     raise UnsupportedSubclassing(
         "Subclassing is not part of referencing's public API. "

referencing/tests/test_core.py

@@ -262,7 +262,7 @@ def test_no_id(self, thing):
     [Registry, Resource, Specification],
 )
 def test_nonsubclassable(cls):
-    with pytest.raises(Exception):
+    with pytest.raises(Exception, match="(?i)subclassing"):  # noqa: B017
 
         class Boom(cls):  # pragma: no cover
             pass