Use approved plan file for apply

[sblack4]

I think ideally, you run the plan you approved instead of applying with -auto-approve. I'm wondering if others feel the same way

I hacked at it a while ago and was able to do it by using artifacts.

• PR with workflow prprprpr sblack4/learning-terraform-github-actions#8
• upload the plan file https://github.com/sblack4/learning-terraform-github-actions/blob/main/.github/workflows/terraform.yaml#L73
• download the plan file https://github.com/sblack4/learning-terraform-github-actions/blob/main/.github/workflows/terraform.yaml#L111