Update CHANGELOG.md

CHANGELOG.md

@@ -9,6 +9,7 @@ The version headers in this history reflect the versions of Apollo Server itself
 
 > The changes noted within this `vNEXT` section have not been released yet.  New PRs and commits which introduce changes should include an entry in this `vNEXT` section as part of their development.  With few exceptions, the format of the entry should follow convention (i.e., prefix with package name, use markdown `backtick formatting` for package names and code, suffix with a link to the change-set à la `[PR #YYY](https://link/pull/YYY)`, etc.).  When a release is being prepared, a new header will be (manually) created below and the appropriate changes within that release will be moved into the new section.
 
+- `apollo-server-lamdbda`: Automatically decode payloads which are Base64-encoded when the `isBase64Encoded` boolean is present on Lambda `event` payloads. [PR #4311](https://github.com/apollographql/apollo-server/pull/4311)
 - The default branch of the repository has been changed to `main`.  As this changed a number of references in the repository's `package.json` and `README.md` files (e.g., for badges, links, etc.), this necessitates a release to publish those changes to npm. [PR #4302](https://github.com/apollographql/apollo-server/pull/4302)
 
 ### v2.15.0