Add certificate_settings to ignore_changes

[socketbox]

Similar to what was done previously for subdomains.

Tested as follows:

1. Created branch in terraform-pbsorg.
2. cd terraform-pbsorg/edcar
3. terraform init
4. terraform plan
5. plan shows this:

Terraform will perform the following actions:

  # module.dotorg_amplify.aws_amplify_domain_association.domain[0] will be updated in-place
  ~ resource "aws_amplify_domain_association" "domain" {
        id                                  = "dgrf2d2vn26dm/edcar.pbs.org"
        # (6 unchanged attributes hidden)

      - certificate_settings {
          - certificate_verification_dns_record = "_4458e50b7235a9c621ee51bc8f91eb35.edcar.pbs.org. CNAME _3a288d5adfc493eeef938e3aad368d5b.shzbfwcggp.acm-validations.aws." -> null
          - type                                = "AMPLIFY_MANAGED" -> null
            # (1 unchanged attribute hidden)
        }

        # (1 unchanged block hidden)
    }

  # module.dotorg_amplify.aws_amplify_domain_association.domain[1] will be updated in-place
  ~ resource "aws_amplify_domain_association" "domain" {
        id                                  = "dgrf2d2vn26dm/pr.pbs.org"
        # (6 unchanged attributes hidden)

      - certificate_settings {
          - certificate_verification_dns_record = "_5b1c37044c3b15b46a1035c4564b2d8f.pr.pbs.org. CNAME _20504ff5432d691bfddecc392aa2e926.sdgjtdhdhz.acm-validations.aws." -> null
          - type                                = "AMPLIFY_MANAGED" -> null
            # (1 unchanged attribute hidden)
        }

        # (10 unchanged blocks hidden)
    }

6. Switch to this branch in amplify module reference.
7. terraform init
8. terraform plan
9. Proposed changes due to certs go away.

[socketbox]

Taking a different tack by adding certificate_settings to the domains object that's passed in.

Update: this ultimately proved fruitless, as I was unable to actually test out if it worked by creating a new Amplify instance. The testing ultimately ended with me being unable to get past this error:

╷
│ Error: creating Amplify App (amplify-test): operation error Amplify: CreateApp, https response error StatusCode: 400, RequestID: ec5c9f36-46f2-4e54-96a8-79deb6641f1f, BadRequestException: There was an issue setting up your repository. Please try again later.({"message":"Not Found","documentation_url":"https://docs.github.com/rest/repos/webhooks#list-repository-webhooks","status":"404"})
│
│   with module.amplify_test.aws_amplify_app.app,
│   on .terraform/modules/amplify_test/main.tf line 1, in resource "aws_amplify_app" "app":
│    1: resource "aws_amplify_app" "app" {
│
╵

For what little it's worth, I've preserved the branch as pass_cert_settings_in.