[backport#10691] Trivial: Properly comment about shutdown process in init.cpp file.

Summary:
581c41157 Properly comment about shutdown process in init.cpp file (Kyuntae Ethan Kim)

Pull request description:

Backport of Core PR10691

Test Plan:

read the comment

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D7791