[test] Add test for getblockheader verboseness
[test] Add test for getblockheader verboseness

Summary:
Add test for getblockheader with verbose argument set to false.

This is a backport of [[https://github.com/bitcoin/bitcoin/pull/19722 | core#19722]]

Test Plan: `ninja check-functional`

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D10120

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