Fix deprecated string interpolation in Analytics.php

[ridonibishi]

Fixes #7169

Changes proposed in this Pull Request

Title: Fix deprecated string interpolation in Analytics.php

Description:
This PR addresses a deprecation issue in /var/www/html/web/app/plugins/woocommerce-payments/includes/multi-currency/Analytics.php. The problem involves the use of ${var} for string interpolation, which is deprecated. This change replaces ${var} with the correct {$var} format, resolving the following warnings:

• Deprecated: Using ${var} in strings is deprecated, use {$var} instead in /plugins/woocommerce-payments/includes/multi-currency/Analytics.php on line 330
• Deprecated: Using ${var} in strings is deprecated, use {$var} instead in /plugins/woocommerce-payments/includes/multi-currency/Analytics.php on line 331
• Deprecated: Using ${var} in strings is deprecated, use {$var} instead in /plugins/woocommerce-payments/includes/multi-currency/Analytics.php on line 332

Testing instructions:
To test this change, follow these steps:

No tests are required because the code changes involve straightforward syntax updates to resolve deprecation warnings. These changes are low-risk and don't introduce new functionality. Visual inspection and basic validation confirm the correctness of the fix. If further testing is required:

1. Clone the repository and switch to the branch with this fix:

   git clone https://github.com/your-username/your-repo.git
   cd your-repo
   git checkout bug-fix

2. Ensure you have the necessary development environment set up for WooCommerce Payments.
3. Locate the Analytics.php file in the multi-currency folder within the WooCommerce Payments plugin.
4. Check lines 330-332 and the suggested fix
5. Identify test cases that previously triggered the deprecation warnings related to string interpolation using ${var}.
6. Execute the identified test cases and confirm that the deprecation warnings no longer appear.
7. Verify that the correct {$var} interpolation is now in place and that the affected code still functions as expected.

---

• Run npm run changelog to add a changelog file (is patch).
• Covered with tests (or have a good reason not to test in description ☝️)
• Tested on mobile (or does not apply)

Post merge

• Link to testing instructions from release testing doc following these instructions: Add link here / 'QA Testing Not Applicable'
• Add or update critical flows and testing instructions for critical flows, if applicable.
• Add what's changed (description, screenshot, demo videos, etc.) to the release announcement post, if applicable.

[dwainm]

Thank you for the PR @ridonibishi ! We'll take a look at it and provide any feedback as soon as possible.

[tpaksu]

The changes make sense, there's no need to test because the alternatives the PR provides were already in use in their previous occurrences. LGTM! And thanks for providing this fix!

[tpaksu]

@ridonibishi can you add a changelog before we merge this to the main repo? You can run npm run changelog after installing the necessary packages. Select patch and skip the message, add your change as a comment (the script will ask after skipping the message), since it's not a big change.

[tpaksu]

I took the initiative and pushed the changelog and added it to the merge queue. Thank you for catching and fixing this!

[ridonibishi]

Sorry - was on a band tour the past 4 days! Thanks for reviewing and patching! Godspeed! 💯