Migarate github actions to Node 16

[tomas-abrahamsson]

The warning message in actions is/was (line-wrapped):

Node.js 12 actions are deprecated. Please update the following actions to use Node.js 16: actions/checkout@v2. For more information see: https://github.blog/changelog/2022-09-22-github-actions-all-actions-will-begin-running-on-node16-instead-of-node12/.

So change from actions/checkout@v2 to v3 which is in the examples that the above page refers to: https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#example-using-versioned-actions

[klajo]

Thanks! I just did a small tweak to the spelling in the title and merged this.