Remove data file installation from setup.py

Manual handling is required due to the inflexibility of distutils.

--- a/setup.py
+++ b/setup.py
@@ -59,11 +59,4 @@ setup(
             "autosuspend = autosuspend:main",
         ],
     },
-    data_files=[
-        ("etc", ["data/autosuspend.conf", "data/autosuspend-logging.conf"]),
-        (
-            "lib/systemd/system",
-            ["data/autosuspend.service", "data/autosuspend-detect-suspend.service"],
-        ),
-    ],
 )
