This removes the explicit disabling of optimization for eval code. Such
code can by now be optimized by TurboFan. Note that the usual heuristics
in the AstNumberingVisitor still apply and will be used to choose the
effective optimization backend.

R=bmeurer@chromium.org

Review-Url: https://codereview.chromium.org/1962103003
Cr-Commit-Position: refs/heads/master@{#36156}