Remove default value for number of threads in Isolate::Init.
Remove default value for number of threads in Isolate::Init.

Just fixing a TODO.

R=jochen@chromium.org

Review URL: https://codereview.chromium.org/978773002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#26987}

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh