[website] Update mining article to use current miner fund address

Summary: It still has the obsolete address

Test Plan: Check the address in an address converter to make sure it's the correct one

Reviewers: Fabien, #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Subscribers: PiRK

Differential Revision: https://reviews.bitcoinabc.org/D13903