Update Terraform docs for deploying the AWS forwarder to use new module

[ktmq]

What does this PR do?

Updates public docs page with guides for installing the forwarder to remove the TF-wrapped cloudformation stack in favor the newly published Terraform module: https://registry.terraform.io/modules/DataDog/log-lambda-forwarder-datadog/aws/latest

Motivation

https://datadoghq.atlassian.net/browse/AWSCORE-345

Testing Guidelines

Additional Notes

Types of changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

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• This PR's description is comprehensive
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