Revert "stages/rpm: truncate the machine id"

This reverts commit 59184b23a2.

This change breaks current testing and is not critical.
We will reintroduce it later when there is time to adapt the tests.

stages/org.osbuild.rpm

@@ -289,11 +289,12 @@ def main(tree, inputs, options):
         enable_dracut(masked_files)
         remove_unowned_etc_kernel(tree)
 
-    # if we created a temporary machine id, replace it with an empty one
+    # remove temporary machine ID if it was created by us
     if not machine_id_set_previously:
-        print("replacing fake machine id with empty one")
+        print("deleting the fake machine id")
         machine_id_file = pathlib.Path(f"{tree}/etc/machine-id")
-        machine_id_file.write_bytes(b"")
+        machine_id_file.unlink()
+        machine_id_file.touch()
 
     # remove random seed from the tree if exists
     with contextlib.suppress(FileNotFoundError):