[chronik-doc] Use the local node for the examples

Summary:
There is now a public node running on the same node, let's use it.

The url scheme is as follow:

• https://chronik-doc.fabien.cash => the public chronik instance
• https://chronik-doc.fabien.cash/docs => the documentation website

Test Plan: Check the remote is responsive and no url has been forgotten.

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Subscribers: bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D16785