Fix 'Ledger search box doesn't support account hierarchy character ":"'

BUG:338306

Test Plan: tested with branch 4.8 and 5.0

Reviewers: #kmymoney

Reviewed By: #kmymoney, tbaumgart

Subscribers: tbaumgart, wojnilowicz

Differential Revision: https://phabricator.kde.org/D8823

(based on commit dc939f28)