t3416: preemptively adjust alignment in a comment

t3416: preemptively adjust alignment in a comment

We are about to adjust t3416 for the new default branch name `main`.
This name is two characters shorter and therefore needs two spaces more
padding to align correctly.

Adjusting the alignment before the big search-and-replace makes it
easier to verify that the final result does not leave any misaligned
lines behind.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>