remove unneeded @cask instancevar in sts.rb

the version method is in scope
remove unneeded @cask instancevar in fenics.rb

the destination_path method is in scope
title for interpolation in alib1
title for interpolation in cdock
title for interpolation in chunkulus
title for interpolation in craftstudio
title for interpolation in delivery-status
title for interpolation in grooveshark
title for interpolation in heart
title for interpolation in intellij-idea-ce
title for interpolation in intellij-idea
title for interpolation in ioquake3
title for interpolation in keycastr
title for interpolation in ksdiff
title for interpolation in pemdas-widget
title for interpolation in qgis
title for interpolation in tv-show-tracker
title for interpolation in tvrenamer
doc: steer away from @cask instance in `caveats`

encourage placements of `caveats` at end of Cask
caveats last in baiduinput