perl-MIME-Base64: removal of module as it is now in the perl core modules

perl-MIME-Base64: removal of module as it is now in the perl core modules

- Used by the git addon.
- With the old separate module removed git still successfully built, installed and was
   able to be run, cloning the ipfire git repo, changing to next, modifying a file and
   the running a commit with the change.

Fixes: bug13640
Tested-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>