[website] Rename Avalanche tutorial blog post

Summary:
The word "staking" is unnecessary and just adds confusion.

Also add a redirect from the previous avalanche tutorial link to make the previous link
(/2022-09-07-avalanche-staking-tutorial) valid as a redirect to the new link (/2022-09-07-avalanche-tutorial).
(from D12297)

Test Plan:
bundle install
bundle exec jekyll serve
Checked that the previous external link works

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D12296