fs: reflink: don't try to reset permissions

We should set desired permissions explicitly in layers above this one.

For now just getting rid of this and proper permissions will be set up
in the followups in `dvc_data.index.checkout`.

Related iterative/dvc-data#274

src/dvc_objects/fs/system.py

@@ -14,10 +14,6 @@
 logger = logging.getLogger(__name__)
 
 
-umask = os.umask(0)
-os.umask(umask)
-
-
 def hardlink(source: "AnyFSPath", link_name: "AnyFSPath") -> None:
     # NOTE: we should really be using `os.link()` here with
     # `follow_symlinks=True`, but unfortunately the implementation is
@@ -107,6 +103,9 @@ def _reflink_linux(src: "AnyFSPath", dst: "AnyFSPath") -> None:
 def reflink(source: "AnyFSPath", link_name: "AnyFSPath") -> None:
     source, link_name = os.fspath(source), os.fspath(link_name)
 
+    # NOTE: reflink may (macos) or may not (linux) clone permissions,
+    # so the user needs to handle those himself.
+
     system = platform.system()
     if system == "Darwin":
         _reflink_darwin(source, link_name)
@@ -118,10 +117,6 @@ def reflink(source: "AnyFSPath", link_name: "AnyFSPath") -> None:
             f"reflink is not supported on '{system}'",
         )
 
-    # NOTE: reflink has a new inode, but has the same mode as the src,
-    # so we need to chmod it to look like a normal copy.
-    os.chmod(link_name, 0o666 & ~umask)
-
 
 def inode(path: "AnyFSPath") -> int:
     return os.lstat(path).st_ino