Fix tflint errors

[melihc1]

Check for latest runs and fix deprecation related errors

Example error: https://github.com/ContainerSolutions/terraform-examples/runs/7654637304?check_suite_focus=true#step:4:1494

Warning: Interpolation-only expressions are deprecated in Terraform v0.12.14 (terraform_deprecated_interpolation)

  on main.tf line 23:
  23:     "${file("values.yaml")}"

Reference: https://github.com/terraform-linters/tflint/blob/v0.39.1/docs/rules/terraform_deprecated_interpolation.md

[melihc1]

Latest version of tflint (v0.40) has many more errors:

https://github.com/ContainerSolutions/terraform-examples/actions/runs/3091438826/jobs/5001511068

Logs uploaded as txt:
logs.txt

[kolja-lucht]

Hey @ttarczynski and @melihc1,
I'd be happy to pick up some of the tflint errors and fix them. Do you have a preferred way of tackling them? Like fix errors of the same kind in one PR or rather go based on in which example they appear or even a different way?