log: Remove static log message "Initializing chainstate Chainstate [ibd] @ height -1 (null)"

Summary:

AFAICT chainstate->ToString() will always equal "Chainstate [ibd] @ height -1 (null)" here which makes the log message neither relevant nor interesting `

This is a backport of core#19984

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D10401