Planning to drop SubjectSpek` in favor of the new `memoized` in <https://github.com/spekframework/s...

# spek

[raniejade]

Planning to drop SubjectSpek` in favor of the new memoized in https://github.com/spekframework/spek/issues/411, it is basically memoized under the hood. It feels a bit redundant now since you can also do TCK-like tests with memoized. Thoughts?