Adjusted indentation in getblockchaininfo's help text to properly align.

Summary:
Adjusted the indentation in the help text of getblockchaininfo to properly align.
Depends on D2730

Test Plan:
make check
bitcoin-cli help getblockchaininfo

Reviewers: deadalnix, jasonbcox, Fabien, O1 Bitcoin ABC, #bitcoin_abc

Reviewed By: Fabien, O1 Bitcoin ABC, #bitcoin_abc

Subscribers: schancel

Differential Revision: https://reviews.bitcoinabc.org/D2737