SetProperty now infers the language mode from the closure and the context
So we no longer have to pass around the language mode. Cleanup by
removing the parameter where it is no longer needed.

Bug: v8:8580
Change-Id: I89452b5a762eb48a911f158d22c7bfa9e3bb1be4
Reviewed-on: https://chromium-review.googlesource.com/c/1421840
Commit-Queue: Mythri Alle <mythria@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59089}