Re-enable mysql-simple in nightly
Re-enable mysql-simple in nightly

Was blocked by `mysql`, which is now back in.
athanclark/stackage,fimad/stackage,mstksg/stackage,massysett/stackage,Daniel-Diaz/stackage,asr/stackage,lwm/stackage,soenkehahn/stackage,wereHamster/stackage,michalkonecny/stackage,fpco/stackage,mgajda/stackage,stackbuilders/stackage,int-index/stackage,spencerjanssen/stackage,iand675/stackage,clinty/stackage,jonschoning/stackage,creichert/stackage,peti/stackage,Shimuuar/stackage,ethercrow/stackage,simonmichael/stackage,mrkkrp/stackage