Move the one remaining optimization disabling in AST numbering (native
function literals) to be in the parser.

Bug: v8:7178
Change-Id: Icd96020622cbe64afa11b42c5831618247e3e021
Reviewed-on: https://chromium-review.googlesource.com/814399
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50170}