[DOCS][AUDIT] redirect any references from https://changelog.optimism.io/ to https://github.com/ethereum-optimism/optimism/releases

[sbvegan]

Is your doc request related to a problem or existing docs? Please describe.

changelog.optimism.io is no longer maintained

Describe the documentation you'd like

• look for any references to that url, the rss feed, and mailing list
• update those references to point to the github release page

Additional context
Add any other context or screenshots about the feature request here.

[cpengilly]

this is done inside new docs and all tech docs will be shifting to the new repo in the next 2-3 weeks, so marking this as done