Vt102EmulationTest: Use QTEST_GUILESS_MAIN

Summary: Allowing the test to pass without a running X server.

Test Plan: Test still passes

Reviewers: #konsole, hindenburg

Reviewed By: #konsole, hindenburg

Subscribers: hindenburg, konsole-devel

Tags: #konsole

Differential Revision: https://phabricator.kde.org/D14539