Update CHANGELOG.md with details from pull request #1978

Obvious fix; these changes are the result of automation not creative thinking.

Author: chef-ci

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
 #### Merged Pull Requests
+- migrating to protobuf-codegen [#1978](https://github.com/habitat-sh/builder/pull/1978) ([mwrock](https://github.com/mwrock))
 - add cargo audit workflow to ci [#1975](https://github.com/habitat-sh/builder/pull/1975) ([mwrock](https://github.com/mwrock))
 - add kernel2 back to default.toml [#1974](https://github.com/habitat-sh/builder/pull/1974) ([mwrock](https://github.com/mwrock))
 - send HAB_AUTH_TOKEN to hab curl bash installer [#1972](https://github.com/habitat-sh/builder/pull/1972) ([mwrock](https://github.com/mwrock))