remove migration cutover security group

[robertsweetman]

• only need to remove the migration_cutover SG this time
• have checked this isn't connected to any instances

[github-actions]

TFSEC Scan Success

Show Output

```hcl

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TFSEC will check the following folders:

</details> #### `Checkov Scan` Success
<details><summary>Show Output</summary>

```hcl

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Checkov will check the following folders:

CTFLint Scan Success

Show Output

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Setting default tflint config...
Running tflint --init...
Installing "terraform" plugin...
Installed "terraform" (source: github.com/terraform-linters/tflint-ruleset-terraform, version: 0.5.0)
tflint will check the following folders:

Trivy Scan

Show Output