Update exercises/raindrops/description.md
Update exercises/raindrops/description.md

Co-Authored-By: Katrina Owen <9131825a40cff71b83fd69ec74e1354ef34ef420@github.com>
petertseng/x-common,ErikSchierboom/x-common,petertseng/x-common,exercism/x-common,jmluy/x-common,ErikSchierboom/x-common,jmluy/x-common,exercism/x-common,jmluy/x-common