Fix crash in FilteredReadStream on task cancellation

[emilk]

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
rust/lance/src/io/exec/filtered_read.rs	0.00%	0 Missing and 1 partial ⚠️

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[westonpace]

This unwrap is doing panic propagation, a panic in the spawned task will propagate into the parent. This is done in quite a few places (e.g. mutexes, other spanwed tasks) throughout the code base. I can see advantages to translating those into errors but I'm curious if there is any particular reason this call site has been a bother?