Revert "Mark diagrams-lib for expected test failure."
Revert "Mark diagrams-lib for expected test failure."

This reverts commit 308cbf6b84c1231493abb030a2a968713d3700f9.

Please see https://github.com/diagrams/diagrams-lib/issues/299#issuecomment-307578324.

mstksg/stackage,asr/stackage,massysett/stackage,lwm/stackage,creichert/stackage,fpco/stackage,peti/stackage,GregorySchwartz/stackage,alanz/stackage,Daniel-Diaz/stackage,ethercrow/stackage,michalkonecny/stackage,garetxe/stackage,Shimuuar/stackage,jonschoning/stackage,phaazon/stackage,mrkkrp/stackage,iand675/stackage,mgajda/stackage,simonmichael/stackage,ygale/stackage,soenkehahn/stackage,wereHamster/stackage,clinty/stackage,athanclark/stackage,spencerjanssen/stackage,fimad/stackage,stackbuilders/stackage,k0ral/stackage,int-index/stackage