[core#19724 2/9][net] Remove unnecessary default args on OpenNetworkConnection

Summary:
This is a backport of core#19724 [2/9]
https://github.com/bitcoin/bitcoin/pull/19724/commits/a6ab1e81f964df131cfa0e11e07bedb3283b823f

Depends on D9770

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Differential Revision: https://reviews.bitcoinabc.org/D9771