test: Update module used for testing init's -from-module feature, so that the test can be run on darwin_arm64 platforms

[SarahFrench]

If you run TestInit_fromModule on an a machine using an Apple chip like M1 then the test will fail like this:

    init_test.go:325: unexpected error: exit status 1
    init_test.go:330: unexpected stderr output:
        ╷
        │ Error: Incompatible provider version
        │ 
        │ Provider registry.terraform.io/hashicorp/template v2.2.0 does not have a
        │ package available for your current platform, darwin_arm64.
        │ 
        │ Provider releases are separate from Terraform CLI releases, so not all
        │ providers are available for all platforms. Other versions of this provider
        │ may have different platforms supported.
        ╵
--- FAIL: TestInit_fromModule (11.28s)

This PR updates the test to use another HashiCorp-owned module that usable on Macbooks etc.

• From: https://registry.terraform.io/modules/hashicorp/vault/aws/latest
• To: https://registry.terraform.io/modules/hashicorp/vault-starter/aws/latest

The test checks that a module can be downloaded when initialising a working directory and it doesn't matter which specific module is in use (as long as it's one we own).

Target Release

N/A

Rollback Plan

• If a change needs to be reverted, we will roll out an update to the code within 7 days.

Changes to Security Controls

Are there any changes to security controls (access controls, encryption, logging) in this pull request? If so, explain.

CHANGELOG entry

• This change is user-facing and I added a changelog entry.
• This change is not user-facing.

[mildwonkey]

works on my machine!!

[github-actions]

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