CallOnBackgroundThread removed from v8-platform

[targos]

See:
https://chromium-review.googlesource.com/c/v8/v8/+/942823
https://chromium-review.googlesource.com/c/v8/v8/+/941944
https://chromium-review.googlesource.com/c/v8/v8/+/1045310

/cc @nodejs/v8-update @addaleax

[targos]

Checkout https://github.com/nodejs/node/tree/canary-base for a branch without the API.

[addaleax]

I think v8/node#69 is what we want for this?

[targos]

Right, that fixes it. Thanks!