The Isolate::context field doesn't track the context while JS is
executing. It's updated at boundary sites when entering runtime
through CEntry or returning to runtime in Invoke(). These set_context
calls are unnecessary.

Bug: v8:8888
Change-Id: Ifb9818b47699d2b1b37ebf0c19c2caf59fd17427
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2247772
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68380}