"Generate latest docs" failing since around the beginning of the month

[cpovirk]

example

...
[gh-pages d130b6a1f] Latest javadoc on successful CI build auto-pushed to gh-pages
 198 files changed, 397 insertions(+), 397 deletions(-)
remote: Permission to google/auto.git denied to github-actions[bot].
fatal: unable to access 'https://github.com/google/auto/': The requested URL returned error: 403
Error: Process completed with exit code 128.

The first failing commit doesn't look particularly suspicious, so maybe there's a token that we need to update or something?