Add link for old release notes

[srirambv]

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Verified that these changes build without errors on
  • Android
  • iOS
  • Linux
  • macOS
  • Windows
• Verified that these changes pass automated tests (unit, browser, security tests) on
  • iOS
  • Linux
  • macOS
  • Windows
• Ran git rebase master (if needed).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Requested a security/privacy review as needed.
• If adding a new directory with NPM packages, ensure this directory is
  added to scripts/audit.js.
• Public documentation has been updated as necessary. For instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protection-Mode
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Custom-Headers
  • https://github.com/brave/brave-browser/wiki/Web-compatibility-issues-with-tracking-protection

Test Plan:

Not adding an issue for the PR as it may be rejected

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Request a security/privacy review as needed.
• Adequate test coverage exists to prevent regressions.

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on.
• All relevant documentation has been updated.

[kjozwiak]

Going to close this off after talking with @bsclifton. We quickly discussed this yesterday about possibly migrating https://github.com/brave/browser-android-tabs/blob/base-80.0.3987.132/CHANGELOG.md into https://github.com/brave/brave-browser/blob/master/CHANGELOG_ANDROID.md. We decided that it's two separate products and we should only mention changes that landed in that specific product rather than confusing users.

Most users get their release notes from either brave.com/latest or reddit/Community per release basis. We'll also have a blog discussing the code base change so community should be aware that it's two different products (at least the ones who actually care about release notes).