Missing test dependency to elm/random

[mpizenberg]

I noticed that elm-test-rs could not run elm-units tests because the tests use the Random module without specifying a test dependency to elm/random. As such, elm-test-rs fails at the compilation step, with the elm compiler complaining about the missing dependency.

Running the tests with elm-test instead of elm-test-rs works fine, but I'd consider that a bug in elm-test and hopefully this gets solved at some point (and a similar issue in elm-test-rs).

Some more details on this category of issues are here: mpizenberg/elm-test-rs#110