Remove comment referencing now fixed Travis bug
Remove comment referencing now fixed Travis bug

The compiler: lines had the effect of getting us separate caches per GHC
version, but since travis-ci/travis-ci#4393 has been fixed we get separate
caches per matrix entry anyway. I left the lines in since they make the build
status pages more readable.

kojiromike/Idris-dev,FranklinChen/Idris-dev,uuhan/Idris-dev,markuspf/Idris-dev,uuhan/Idris-dev,eklavya/Idris-dev,jmitchell/Idris-dev,jmitchell/Idris-dev,eklavya/Idris-dev,jmitchell/Idris-dev,uuhan/Idris-dev,markuspf/Idris-dev,FranklinChen/Idris-dev,FranklinChen/Idris-dev,bravit/Idris-dev,bravit/Idris-dev,kojiromike/Idris-dev,mpkh/Idris-dev,eklavya/Idris-dev,jmitchell/Idris-dev,markuspf/Idris-dev,uuhan/Idris-dev,Heather/Idris-dev,bravit/Idris-dev,mpkh/Idris-dev,Heather/Idris-dev,FranklinChen/Idris-dev,FranklinChen/Idris-dev,uuhan/Idris-dev,markuspf/Idris-dev,Heather/Idris-dev,bravit/Idris-dev,kojiromike/Idris-dev,uuhan/Idris-dev,kojiromike/Idris-dev,kojiromike/Idris-dev,mpkh/Idris-dev,jmitchell/Idris-dev,mpkh/Idris-dev,eklavya/Idris-dev,uuhan/Idris-dev,jmitchell/Idris-dev,Heather/Idris-dev,bravit/Idris-dev,markuspf/Idris-dev,mpkh/Idris-dev,Heather/Idris-dev,FranklinChen/Idris-dev,mpkh/Idris-dev,kojiromike/Idris-dev,bravit/Idris-dev,markuspf/Idris-dev,eklavya/Idris-dev,markuspf/Idris-dev,eklavya/Idris-dev,Heather/Idris-dev