وَالْقَهْقَهَةُ فِي كُلِّ صَلَاةٍ ذَاتِ رُكُوعٍ وَسُجُودٍ
Translation: Loud laughter in every prayer containing bowing and prostration.
The restriction means that the specific wudu ruling applies in the stated prayer setting, rather than to every laugh outside prayer or every form of worship.