doc: correct logging rpc return type and example

Summary:
logging status is returned as a bool, not 0|1

Backport of Core PR15272

Test Plan:

ninja && sudo ninja install
bitcoin-cli help logging
bitcoin-cli logging "[\"all\"]" "[\"http\"]"

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, deadalnix

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D7702