🐛🧪 Fix the operator in test_lt

It was incorrectly testing the `<=` twice which resulted in missing
coverage for `<` in the Cython module.

tests/test_frozenlist.py

@@ -88,7 +88,7 @@ def test_le(self) -> None:
 
     def test_lt(self) -> None:
         _list = self.FrozenList([1])
-        assert _list <= [3]
+        assert _list < [3]
 
     def test_ge(self) -> None:
         _list = self.FrozenList([1])