fix #18002

[dylan-conway]

What does this PR do?

AsyncContextFrame does not pass an isCallable() check, making napi_call_function return napi_invalid_arg. I'm not sure this is the best way to do this. Ideally JSC should see AsyncContextFrame as callable so nothing needs to change here.

Fixes #18002

How did you verify your code works?

[robobun]

^{Updated 1:06 PM PT - Apr 7th, 2025}

❌ @dylan-conway, your commit 0aa93d0 has 2 failures in Build #14567:

• test/js/bun/spawn/spawn.test.ts - 1 failing on 🐧 3.21 x64-baseline
• test/js/web/fetch/fetch.test.ts - 1 failing on 🍎 14 aarch64

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🧪   try this PR locally:

bunx bun-pr 18832