Payments Button block: change wording of payment button 'exclusive member updates'

### Impacted plugin

Jetpack

### Steps to Reproduce

1. Create a new post and add a payments button block
2. Manage the payment plans https://wordpress.com/earn/payments-plans/
3. Find the plan associated with the button in the list ➡ three dots ➡ edit
4. Click the Email tab
5. Toggle _Email newly published posts to your customers._ and save
6. View the post
7. Press the payment button

### A clear and concise description of what you expected to happen.

- Form to enter my payment details
- Checkbox about receiving email updates

### What actually happened

* Form to enter my payment details ✅
* Form has field saying 'Sign me up to receive exclusive member updates'
*

### Other information

It appears that the original intention of this functionality was for the premium-content block, in which case it doesn't actually send exclusive member updates as such, but sends out blog posts where the premium-content block will display subscriber/guest content as appropriate.

People now use the payment button for many different reasons, including donations. They don't necessarily want to offer exclusive member updates, but might want people to be able to receive email updates of every post they send.

There's a stale related [issue about removing the checkbox entirely](https://github.com/Automattic/wp-calypso/issues/41597)

The wording of the checkbox comes from `wp-content/lib/memberships/templates/screen-main.php` and `wp-content/lib/memberships/templates/screen-code.php` on wpcom

### Operating System

_No response_

### OS Version

_No response_

### Browser

Firefox

### Browser Version(s)

_No response_

Start with wp-content/lib/memberships/templates/screen-main.php and wp-content/lib/memberships/templates/screen-code.php, where the checkbox wording is defined. Reproduce the Payments Button flow described in the issue, then determine the replacement wording with the maintainer before editing. Done means the payment form shows accurate, non-misleading email-update text in the affected flow.

Written by the indexing model from the issue text.