Forms: fix permission check in Responses endpoint

[jeherve]

Proposed changes:

• This is a follow-up to Add form responses v2 endpoint #29043. When registering the endpoint, we used the wrong parameter to define permissions.

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

• N/A

Does this pull request change what data or activity we track or use?

• No

Testing instructions:

Start by enabling the new Forms interface, by adding the following to a functionality plugin:

add_filter( 'jetpack_contact_form_use_package', '__return_true' );
add_filter( 'jetpack_forms_dashboard_enable', '__return_true' );

Then, before you check out this branch:

1. Go to https://yoursite.com/wp-json/wpcom/v2/forms/responses
2. View responses, even though you are not authenticated.
3. Check out this branch, and reload the page above.
4. Get a permission error.
5. In wp-admin, go to the Feedback menu.
6. In your browser console, fetch responses and check that they are all returned: wp.apiFetch({path: '/wpcom/v2/forms/responses'}).then(r=>console.log(r))

[github-actions]

Are you an Automattician? You can now test your Pull Request on WordPress.com. On your sandbox, run

bin/jetpack-downloader test jetpack fix/forms-endpoint-permissions

to get started. More details: p9dueE-5Nn-p2

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

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[CGastrell]

Oopsie!

LGTM!