Replace lambda `repr` filters with `bool`

[pomponchik]

Blocked by mutating/sigmatch#17.

CI failure with the original bool filters:
https://github.com/mutating/cantok/actions/runs/28411635113/job/84185622935?pr=57#logs

AbstractToken.__repr__ uses lambdas only because bool currently raises
sigmatch.errors.SignatureNotFoundError through printo.describe_call on
Python 3.11.

After sigmatch supports matching built-in callables, replace the workaround:

diff --git a/cantok/tokens/abstract/abstract_token.py b/cantok/tokens/abstract/abstract_token.py
@@
             filters={
-                0: lambda argument: bool(argument),
-                'cancelled': lambda argument: bool(argument),
+                0: bool,
+                'cancelled': bool,
                 'doc': not_none,
             },

Verify on Python 3.11 that repr(SimpleToken()) == 'SimpleToken()' and the test
suite still passes.