Node 12 warnings

[dougch]

We're seeing warnings about the use of node 12 in this action:

Node.js 12 actions are deprecated. Please update the following actions to use Node.js 16: ethomson/issue-dashboard@v1. 

For more information, see https://github.blog/changelog/2022-09-22-github-actions-all-actions-will-begin-running-on-node16-instead-of-node12

Also an across the board update to checkout@v3 is needed: https://github.com/marketplace/actions/checkout