ovl: update doc

Some of the documented quirks no longer apply.
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>

Documentation/filesystems/overlayfs.txt

@@ -183,12 +183,10 @@ The copy_up operation essentially creates a new, identical file and
 moves it over to the old name.  The new file may be on a different
 filesystem, so both st_dev and st_ino of the file may change.
 
-Any open files referring to this inode will access the old data and
-metadata.  Similarly any file locks obtained before copy_up will not
-apply to the copied up file.
+Any open files referring to this inode will access the old data.
 
-On a file opened with O_RDONLY fchmod(2), fchown(2), futimesat(2) and
-fsetxattr(2) will fail with EROFS.
+Any file locks (and leases) obtained before copy_up will not apply
+to the copied up file.
 
 If a file with multiple hard links is copied up, then this will
 "break" the link.  Changes will not be propagated to other names