Incorrectly hitting IS_MAYBE_MIRAGE

[kategengler]

I'm attempting to move to Request Handlers but when I attempt to modify headers I'm hitting:

Failed to execute 'set' on 'Headers': Headers are immutable

it is coming from:

https://github.com/warp-drive-data/warp-drive/blob/main/warp-drive-packages/core/src/request/-private/fetch.ts#L143

window.fetch in my project is indeed patched, by Sentry, not mirage. There are so many things that patch fetch -- this really cannot be a determiner of mirage.