Relax aff dependency version (#58)

Because spec test dependency needs aff <8.0.0

Author: jamesdbrock

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ jobs:
 
       - uses: purescript-contrib/setup-purescript@main
         with:
-          purescript: "unstable"
+          purescript: "latest"
           purs-tidy: "latest"
           spago: "unstable"