bump sbt version in the migration guide
bump sbt version in the migration guide

zaneli/playframework,playframework/playframework,rajeshpg/playframework,hagl/playframework,playframework/playframework,wegtam/playframework,ktoso/playframework,mkurz/playframework,wsargent/playframework,wegtam/playframework,Shruti9520/playframework,wegtam/playframework,Shenker93/playframework,aradchykov/playframework,Shenker93/playframework,ktoso/playframework,Shruti9520/playframework,zaneli/playframework,richdougherty/playframework,wegtam/playframework,wsargent/playframework,mkurz/playframework,rajeshpg/playframework,rajeshpg/playframework,richdougherty/playframework,Shruti9520/playframework,Shruti9520/playframework,richdougherty/playframework,zaneli/playframework,zaneli/playframework,playframework/playframework,wsargent/playframework,benmccann/playframework,ktoso/playframework,Shenker93/playframework,Shenker93/playframework,ktoso/playframework,benmccann/playframework,hagl/playframework,benmccann/playframework,benmccann/playframework,wsargent/playframework,rajeshpg/playframework,aradchykov/playframework,aradchykov/playframework,marcospereira/playframework,aradchykov/playframework,marcospereira/playframework,marcospereira/playframework,hagl/playframework,mkurz/playframework,hagl/playframework,mkurz/playframework,marcospereira/playframework,richdougherty/playframework