chore: remove expired v0.3.1 compatibility shims (#5106)

tests/channels/test_channel_plugins.py

@@ -788,35 +788,6 @@ def test_discover_plugins_skips_names_outside_enabled_set():
     assert loaded == []
 
 
-def test_discover_plugins_warns_once_for_legacy_entry_points():
-    from nanobot.channels.registry import _warn_legacy_channel_entry_points, discover_plugins
-
-    legacy_entry_points = [SimpleNamespace(name="z-old"), SimpleNamespace(name="a-old")]
-    _warn_legacy_channel_entry_points.cache_clear()
-    try:
-        with (
-            patch(
-                "nanobot.channels.registry.entry_points",
-                return_value=legacy_entry_points,
-            ) as metadata_entry_points,
-            patch("nanobot.channels.registry._channel_package_names", return_value=[]),
-            patch("nanobot.channels.registry.logger.warning") as warning,
-        ):
-            discover_plugins()
-            discover_plugins()
-    finally:
-        _warn_legacy_channel_entry_points.cache_clear()
-
-    metadata_entry_points.assert_called_once_with(group="nanobot.channels")
-    warning.assert_called_once_with(
-        "Legacy channel entry points were detected but will not be loaded: {}. "
-        "The '{}' entry-point group is no longer supported; use a built-in channel or "
-        "migrate it into nanobot/channels/<channel>/.",
-        "a-old, z-old",
-        "nanobot.channels",
-    )
-
-
 def test_channel_manifest_rejects_invalid_dependency_metadata():
     with pytest.raises(TypeError, match="tuple of requirements"):
         ChannelPlugin(