Remove extra newline that leads to linter warning

Summary:
D3979 removed the freopen() function and leaded to an extra newline.
Most likely the linter did some other autofix that made this being
hidden at submission time.

Test Plan:
Should return no error:

arc lint --everything

Reviewers: #bitcoin_abc, deadalnix, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D3999