Use sbt 1.5 syntax for dumpStructureTo

[akozich]

With sbt 1.5+ I started receiving warnings while reloading sbt project in Idea

[warn] sbt 0.13 shell syntax is deprecated; use slash syntax instead: Global / dumpStructureTo

This happens because sbt 1.5 deprecated sbt 0.13 syntax with : separator

Here's the ticket SCL-18893