Removed old version of SortedSet from `base`.
Removed old version of SortedSet from `base`.

markuspf/Idris-dev,mpkh/Idris-dev,Heather/Idris-dev,Heather/Idris-dev,mpkh/Idris-dev,kojiromike/Idris-dev,markuspf/Idris-dev,markuspf/Idris-dev,kojiromike/Idris-dev,mpkh/Idris-dev,kojiromike/Idris-dev,uuhan/Idris-dev,uuhan/Idris-dev,Heather/Idris-dev,FranklinChen/Idris-dev,uuhan/Idris-dev,Heather/Idris-dev,uuhan/Idris-dev,kojiromike/Idris-dev,FranklinChen/Idris-dev,uuhan/Idris-dev,mpkh/Idris-dev,uuhan/Idris-dev,mpkh/Idris-dev,kojiromike/Idris-dev,markuspf/Idris-dev,FranklinChen/Idris-dev,FranklinChen/Idris-dev,markuspf/Idris-dev,Heather/Idris-dev,FranklinChen/Idris-dev,Heather/Idris-dev,markuspf/Idris-dev,FranklinChen/Idris-dev,mpkh/Idris-dev,uuhan/Idris-dev,markuspf/Idris-dev,kojiromike/Idris-dev