Fix failing test.

Index: tests/test_unix.py
--- tests/test_unix.py.orig
+++ tests/test_unix.py
@@ -97,7 +97,7 @@ def _func_to_path(func: str) -> XDGVariable | None:
         "user_cache_dir": XDGVariable("XDG_CACHE_HOME", "~/.cache"),
         "user_state_dir": XDGVariable("XDG_STATE_HOME", "~/.local/state"),
         "user_log_dir": XDGVariable("XDG_STATE_HOME", "~/.local/state"),
-        "user_runtime_dir": XDGVariable("XDG_RUNTIME_DIR", "/run/user/1234"),
+        "user_runtime_dir": XDGVariable("XDG_RUNTIME_DIR", "/tmp/runtime-1234"),
     }
     return mapping.get(func)