update changelog docs

Author: chargome

CONTRIBUTING.md

@@ -81,10 +81,10 @@ _These steps are only relevant to Sentry employees when preparing and publishing
 ### Updating the Changelog
 
 1. Create a new branch.
-2. Run `git log --format="- %s"` and copy everything since the last release.
+2. Run `yarn changelog` and copy all commits in the list.
 3. Create a new section in the changelog, deciding based on the changes whether it should be a minor bump or a patch release.
-4. Paste in the logs you copied earlier.
+4. Paste in the commits you copied earlier.
 5. Delete any which aren't user-facing changes.
 6. Alphabetize the rest.
 7. If any of the PRs are from external contributors, include underneath the commits `Work in this release contributed by <list of external contributors' GitHub usernames>. Thank you for your contributions!`. If there's only one external PR, don't forget to remove the final `s`. If there are three or more, use an Oxford comma. (It's in the Sentry styleguide!)
-8. Commit, push, and open a PR with the title `meta: Update changelog for <fill in relevant version here>`.
+8. Commit, push, and open a PR against `main` with the title `meta: Update changelog for <fill in relevant version here>`.