Remove unused argument to ThreadHTTP(...)
Remove unused argument to ThreadHTTP(...)

Summary:
Partial backport of Core PR13554 (the other commits do not apply to ABC)
https://github.com/bitcoin/bitcoin/pull/13554/commits/05dbb0c042ba647bf83c15f059c41620e2164337
Completes T538

Test Plan: ninja check

Reviewers: deadalnix, Fabien, Mengerian, #bitcoin_abc

Reviewed By: Fabien, #bitcoin_abc

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2587

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