Coupon codes not showing in invoice print out #9216

[naouibelgacem]

Description

fix issue #9216
Coupon codes not showing in invoice print out

Fixed Issues (if relevant)

1. Coupon codes not showing in invoice print out #9216: Issue title
2. ...

Manual testing scenarios

1. Login to admin.
2. Create a coupon.
3. Go to frontend / Make an order make sure you use the coupon.
4. Back to admin create an invoice on the purchased order.
5. Print Invoice.

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[magento-cicd2]

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