allow arbirary types in set.discard

[randolf-scholz]

Fixes #15271

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

core (https://github.com/home-assistant/core)
+ homeassistant/core_config.py:529: error: Argument 1 of "discard" is incompatible with supertype "builtins.set"; supertype defines the argument type as "object"  [override]
+ homeassistant/core_config.py:529: note: This violates the Liskov substitution principle
+ homeassistant/core_config.py:529: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#incompatible-overrides

[randolf-scholz]

Homeassistent error is harmless:

class _ComponentSet(set[str]):
    def discard(self, value: str) -> None:
        """Remove a component from the store."""
        raise NotImplementedError("_ComponentSet does not support discard, use remove")

they just need to update to object.