Update ConfirmSubscription.php

[Corepex]

Updated Example according to API docs

aws-doc-sdk-examples Pull Request

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NOTE: This PR template contains three sections. Depending on the reason for your pull request, please fill out the section that applies to you and then remove the other two sections.

Existing Example Update

The submitter has:

Updated the example according to the api docs.
https://docs.aws.amazon.com/sns/latest/api/API_ConfirmSubscription.html

• Confirmed that the correct copyright is included in all files.
• Changed or added comments and strings have been reviewed, and the submitter has incorporated any and all suggested edits.
• Major code changes have been reviewed, and the submitter has incorporated review comments.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[beqqrry-aws]

The linting errors can be safely ignored for this PR.