Change Text Selection icon to edit-select-text

Summary:
The current icon (draw-text) is semantically incorrect. This patch makes the Text Selection tool use the icons added in D21632.

BUG: 408391
FIXED-IN: 1.8.0

Test Plan: {F6874885, size=full}

Reviewers: #vdg, #okular, ngraham

Reviewed By: #vdg, ngraham

Subscribers: okular-devel

Tags: #okular

Differential Revision: https://phabricator.kde.org/D21633