fix: remove dead-code Python version guard in utils/__init__.py (#270)

The guard:
    if sys.version_info.major == 3 and sys.version_info.minor >= 3:
        from collections.abc import MutableMapping
    else:
        from collections.abc import MutableMapping

has identical branches — both import from collections.abc (the correct
Python 3.3+ location).  Remove the guard; keep the bare import.

Closes #251

ChangeLog.md

@@ -12,6 +12,8 @@ Generated by [`auto-changelog`](https://github.com/CookPete/auto-changelog).
 
 - Enable ruff isort (I) ruleset in pyproject.toml [`a3801f6`](https://github.com/craigerl/aprsd/commit/a3801f6)
 
+- Remove dead-code Python version guard in utils/__init__.py: both branches were identical [`aa43f60`](https://github.com/craigerl/aprsd/commit/aa43f60)
+
 - Add reset() to @singleton decorator; update tests to use ClassName.reset() instead of ClassName.instance = None [`ef19aaa`](https://github.com/craigerl/aprsd/commit/ef19aaa)
 
 - Fix PacketTrack.keys/items/values — return list snapshots instead of live dict views outside the lock [`088436e`](https://github.com/craigerl/aprsd/commit/088436e)

aprsd/utils/__init__.py

@@ -7,6 +7,7 @@ import os
 import re
 import sys
 import traceback
+from collections.abc import MutableMapping
 
 import update_checker
 
@@ -18,11 +19,6 @@ from .fuzzyclock import fuzzy  # noqa: F401
 # aprsd.utils
 from .ring_buffer import RingBuffer  # noqa: F401
 
-if sys.version_info.major == 3 and sys.version_info.minor >= 3:
-    from collections.abc import MutableMapping
-else:
-    from collections.abc import MutableMapping
-
 
 def singleton(cls):
     """Make a class a Singleton class (only one instance).

tests/utils/test_utils.py

@@ -323,3 +323,22 @@ class TestUtils(unittest.TestCase):
         level, msg = utils._check_version()
         self.assertEqual(level, 1)
         self.assertEqual(msg, 'New version available')
+
+
+class TestDeadCodeRemoval(unittest.TestCase):
+    """Regression tests for dead code that was removed."""
+
+    def test_mutable_mapping_importable(self):
+        """MutableMapping must be importable from aprsd.utils after dead-code removal.
+
+        The version guard
+            if sys.version_info.major == 3 and sys.version_info.minor >= 3:
+                from collections.abc import MutableMapping
+            else:
+                from collections.abc import MutableMapping
+        had both branches do the same thing.  After removing the guard the import
+        must still succeed on all supported Python versions.
+        """
+        from aprsd.utils import MutableMapping as MM  # noqa: N814
+
+        self.assertTrue(issubclass(dict, MM))