Fix regression for user config files (python#18656)

Fixes python#18650

Slightly annoying to add a test for since it would clutter up user home
directory

Author: hauntsaninja

mypy/defaults.py

@@ -17,9 +17,10 @@
 CONFIG_NAMES: Final = ["mypy.ini", ".mypy.ini"]
 SHARED_CONFIG_NAMES: Final = ["pyproject.toml", "setup.cfg"]
 
-USER_CONFIG_FILES: Final = ["~/.config/mypy/config", "~/.mypy.ini"]
+USER_CONFIG_FILES: list[str] = ["~/.config/mypy/config", "~/.mypy.ini"]
 if os.environ.get("XDG_CONFIG_HOME"):
     USER_CONFIG_FILES.insert(0, os.path.join(os.environ["XDG_CONFIG_HOME"], "mypy/config"))
+USER_CONFIG_FILES = [os.path.expanduser(f) for f in USER_CONFIG_FILES]
 
 # This must include all reporters defined in mypy.report. This is defined here
 # to make reporter names available without importing mypy.report -- this speeds