unbreak windows build

Summary:
In D9522, I didn't remove all occurences of boost::this_thread::interruption_point();. It did not break the linux build, but it broke the Windows build.
Remove the last remaining occurence of boost::this_thread::interruption_point();.

Test Plan:
grep -r "boost::this_thread" src/

ninja all check-all

@bot build-win

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D9528