Backport of Remove Interpolation-only expressions from website/docs files into v1.7

[github-actions]

Backport

This PR is auto-generated from #36065 to be assessed for backporting due to the inclusion of the label 1.7-backport.

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The person who merged in the original PR is:
@radeksimko
This person should manually cherry-pick the original PR into a new backport PR,
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merge conflict error: POST https://api.github.com/repos/hashicorp/terraform/merges: 409 Merge conflict []

The below text is copied from the body of the original PR.

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Interpolation-only expressions are deprecated in Terraform v0.12.14.
See. terraform_deprecated_interpolation - tflint-ruleset-terraform

Fixes #36064

Target Release

1.x.x

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Overview of commits

• 26a478c

• f56b8db

• b8692d3

• 2c203e3

• e93895b

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[radeksimko]

This doesn't necessarily have to be back-ported, it was just a best-effort attempt anyway.