Striking prices for variations similar to how we do for simple products.

[ideadude]

All Submissions:

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

Changes proposed in this Pull Request:

Before this update, when you chose a variation from the dropdown on the frontend, you would see the variation price like: $10.00 $10.00. There was a strikethrough, but the sale price was not shown.

This update allows our strikethrough code to work on variations like it does on simple products (the variable products still show a range).

How to test the changes in this Pull Request:

1. Create a variable product with a few variations.
2. Set up a coupon and SWS that applies to that product.
3. Visit the product on the frontend and choose a variation.

It should show the discounted price now.

Other information:

• [x] Have you added an explanation of what your changes do and why you'd like us to include them?
• [x] Have you successfully run tests with your changes locally?

Changelog entry

BUG FIX: Now striking prices for variations similar to how we do for simple products.