Use logically correct icon for direction arrows

Test Plan:
Before:
{F6626036}
After:
{F6626027}

Reviewers: #vdg, ngraham, #okular

Reviewed By: #vdg, ngraham

Subscribers: aacid, abetts, davidhurka, ngraham, okular-devel

Tags: #okular

Differential Revision: https://phabricator.kde.org/D19183