Hello

I had problems with product import.
After some time, I managed to identify that CSV keys with line breaks cause the import to skip the column, while the mapping looks like it should have worked.
The PR remove line breaks in the keys of the CSV imported file, to avoid mismatch mapping of keys.

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 PR fixes product import when the CSV imported file has a line break in a key name.
If a key has a line break, mapping fields will look OK, but the import will simply skip the values of this key.

Example of a CSV file with line break below:

ID,Published,"Regular 
price"
3011,1,168

With a line break, the mapping looks like it will work (image below):

The PR removes line breaks in all the CSV keys.
Regular\nprice becomes Regular price.

• This PR is a very minor change/addition and does not require testing instructions (if checked you can ignore/remove the next section).

How to test the changes in this Pull Request:

1. Export the products using WC core tool
2. In the CSV file, add a line break inside the key Regular price
3. Change the price of some products
4. Keep the columns: ID, Published, Regular price, and remove the others
5. Use the product import tool and map the 3 fields
6. After it is done, the price should be be updated thanks to the PR. Without the PR, prices won't be updated

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 created a changelog file for each project being changed, ie pnpm --filter=<project> changelog add?

FOR PR REVIEWER ONLY:

• I have reviewed that everything is sanitized/escaped appropriately for any SQL or XSS injection possibilities. I made sure Linting is not ignored or disabled.