Fix boxplottertester
OpenGL was unnecessarily added to the project. This caused the build to
fail for VxWorks. The 'opengl' is removed from the project.
Task-number: QTRD-2159
Change-Id: Ic330f7e65661affd024c5204ae425812aea42c41
Reviewed-by: Karim Pinter <karim.pinter@digia.com>
Reviewed-by: Mika Salmela <mika.salmela@digia.com>