docs: Update changelog to 3.0

[presatish]

If your build fails due to your commit message not passing the build checks, please review the guidelines here: https://github.com/edgexfoundry/edgex-go/blob/main/.github/Contributing.md

PR Checklist

Please check if your PR fulfills the following requirements:

• [x] I am not introducing a breaking change (if you are, flag in conventional commit message with BREAKING CHANGE: describing the break)
• [x] I am not introducing a new dependency (add notes below if you are)
• [ ] I have added unit tests for the new feature or bug fix (if not, why?)
• [ ] I have fully tested (add details below) this the new feature or bug fix (if not, why?)
• [ ] I have opened a PR for the related docs change (if not, why?)

Testing Instructions

New Dependency Instructions (If applicable)

[codecov-commenter]

Codecov Report

Merging #372 (386e6c7) into main (c742c11) will not change coverage. The diff coverage is n/a.

:exclamation: Current head 386e6c7 differs from pull request most recent head 9c83e7b. Consider uploading reports for the commit 9c83e7b to get more accurate results

:exclamation: Your organization is not using the GitHub App Integration. As a result you may experience degraded service beginning May 15th. Please install the Github App Integration for your organization. Read more.

@@           Coverage Diff           @@
##             main     #372   +/-   ##
=======================================
  Coverage   34.09%   34.09%           
=======================================
  Files          19       19           
  Lines        1804     1804           
=======================================
  Hits          615      615           
  Misses       1123     1123           
  Partials       66       66