mail/dovecot-fts-flatcurve: update to 1.0.2

Update dovecot-fts-flatcurve to the current stable release.

Full changelog: https://github.com/slusarz/dovecot-fts-flatcurve/compare/v1.0.0...v1.0.2

Major changes:

Per upstream, Fix assert-crash in certain instances when doing
multi-mailbox searches (e.g., virtual mailbox search)

PR: 277682
Reported by: Martin Waschbüsch <martin@waschbuesch.de> (maintainer)