libc/glibc: remove dead code

The option to retrieve snapshots is already handled by
the generic 'specific date' and 'use latest' entries.
No need for a special case, as there's no code for it.

 reporter_name="Nye Liu"

 reporter_url="http://sourceware.org/ml/crossgcc/2008-10/msg00046.html"

 reporter_comment=""