Drop [RuntimeEnabled] for all IDL dictionaries

Like enums, typedefs, etc., dictionaries aren't observable unless used,
and the generated code does not change by removing [RuntimeEnabled].

R=bashi@chromium.org

Review-Url: https://codereview.chromium.org/2390483002
Cr-Commit-Position: refs/heads/master@{#427039}
20 files changed