Remove Emoji from default additional email content

[claudiosanches]

All Submissions:

• Have you followed the WooCommerce Contributing guideline?
• Does your code follow the WordPress' coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

This doesn't affect all installations, since this issue depends on the database structure, not all WordPress installations properly support emojis, this will stop email settings to get saved, so it's easy to just remove this emoji for now.

Closes #24405.

How to test the changes in this Pull Request:

1. Since this not affect all installations may become hard to test, but you can try change the database to something else that is not utf8mb4.
2. Try save the settings with an emoji like 🙌, this may stop the page get saved, you can try reload or access the URL again: wp-admin/admin.php?page=wc-settings&tab=email&section=wc_email_new_order
3. And now the only way to save is to remove all emojis from the content.

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully run tests with your changes locally?

Changelog entry

Fix - Removed Emoji from default additional email content due problem on some database that doesn't allow Emojis.

[codecov]

Codecov Report

Merging #24450 into master will decrease coverage by <.01%.
The diff coverage is 100%.

Impacted Files	Coverage Δ	Complexity Δ
includes/emails/class-wc-email-new-order.php	70.11% <100%> (ø)	13 <0> (ø)	⬇️
...shipping/flat-rate/includes/settings-flat-rate.php	91.84% <0%> (-4.08%)	0% <0%> (ø)

[vedanshujain]

LGTM!