chore: update file headers (#515)

* changes without context

        autosynth cannot find the source of changes triggered by earlier changes in this
        repository, or by version upgrades to tools such as linters.

* chore: modify synth excludes

Co-authored-by: Bu Sun Kim <busunkim@google.com>
Co-authored-by: Bu Sun Kim <8822365+busunkim96@users.noreply.github.com>
5 files changed