Drop reference to webrtc_overrides/.../task_queue.h
Drop reference to webrtc_overrides/.../task_queue.h

Since cl
https://chromium-review.googlesource.com/c/chromium/src/+/664807,
chromium no longer uses it. We need to stop referring to it from
webrtc, before it can be deleted in chromium.

BUG=webrtc:8166

Review-Url: https://codereview.webrtc.org/3015513002
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#19901}

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