[backport#15901 2/2] remove extraneous scope

Summary:
https://github.com/bitcoin/bitcoin/pull/15901/commits/1b602f6fed2a6a03fd4d463bc56fa9eb0c4c779c

(note: easier visualized by hiding whitespace changes. in fact I reset
the incoming changes from Core, removed the two brackets and formatted.
less error prone that way.)

Depends on D7032

Concludes backport of Core PR15901

Test Plan:

ninja check check-functional

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D7033