misc: change add distance image for sightviewer test sensitivity

Description

The initial image stored as reference for sightviewer gui test addDistance was too permisive. When compared to a failed addDistance, it was still a success.

The new one is more restricitve.

Related to sight#1069 (closed)

How to test it?

run .\bin\sightviewerguitest.bat sight::sightviewer::test::ui::AddDistance in sight on the associated branch