Bug 29501: Remove MIME::Lite dependency

Bug 29501: Remove MIME::Lite dependency

The library usage is discouraged by the current maintainer and we don't
use it in the codebase anymore.

To test:
1. Apply this patch
2. Run:
   $ git grep MIME::Lite
=> SUCCESS: No uses of the removed library
3. Sign off :-D

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>