Update CircleCI gh-pages deploy key

[whd]

Background #732

https://app.circleci.com/settings/project/github/mozilla/gcp-ingestion/ssh?return-to=https%3A%2F%2Fapp.circleci.com%2Fpipelines%2Fgithub%2Fmozilla%2Fgcp-ingestion%3Ffilter%3Dall

It looks like (from a :jason screenshot) this deploy key is possibly associated with :wlach, and is separate from the main deploy key. I'm not sure what the details here are, but the current key seems to work correctly.

I suspect we should switch to an ops-managed key for this, but I would need to look into this a bit more to understand how/why it's configured the way it is.