fix plural in problem text, fix #47643

*isSingular(randRange( 1, 8 ))* and *<var>randRange( 1, 8 )</var> hour/s* are different numbers. i added a new variable *sleddingHours* and use it as *<var>sleddingHours</var> <var>plural("hour", sleddingHours)</var>*
Merge pull request #52187 from mauk81/patch-2

fix plural in problem text, fix #47643