Remove MOVED_LIBS handling from list-old-libs

In 922337e8d398 I added MOVED_LIBS into list-old-files, so that
delete-old-files would remove the old /usr/lib/libc++.so.1 as soon as
possible (after the library moved to /lib).

I left it in list-old-libs in case a user updated their src tree between
delete-old-files and delete-old-libs. Now that some time has passed,
tremove the redundant MOVED_LIBS entry.

PR: 272642
Sponsored by: The FreeBSD Foundation