Don't trigger documentation/benchmarks upload if user is dependabot

[jasonwilliams]

Workflows triggered by Dependabot PRs will run with read-only permissions

We should set out workflow file to not bother uploading anything when the master-merge was by dependabot.
We should be able to use an if statement in the build block. Similar to https://docs.github.com/en/actions/reference/context-and-expression-syntax-for-github-actions#determining-when-to-use-contexts

Maybe ${{ github.actor !== "dependabot"}} or something