media-fonts/symbola: Update LICENSE, add mirror restriction.

media-fonts/symbola: Update LICENSE, add mirror restriction.

The last version distributed under the "Unicode_Fonts_for_Ancient_Scripts"
terms was symbola-7.17, see the Wayback Machine:
https://web.archive.org/web/20141027122717/http://users.teilar.gr/~g1951d/

Versions from 7.18 to 10.24 were distributed under "free for any use"
terms, and upstream has explicitly refused to clarify if this includes
the right to modify and/or redistribute. This is not better than not
having any license at all (i.e., "all-rights-reserved").

Later versions (after 10.24) are even more restrictive and e.g. have a
non-commercial and non-educational clause.

Bug: https://bugs.gentoo.org/715226
Package-Manager: Portage-2.3.96, Repoman-2.3.22
Signed-off-by: Ulrich Müller <ulm@gentoo.org>