[Forwardport2.3] Fix incorrect type hinting in PHPDocs

[chirag-wagento]

Original Pull Request

#15619

Description

Incorrect PHPdoc causes warnings in IDE.

Changes applied:

1. Changed the return type for setQty method to the type it actually returns.
2. Removed the hint for newer thrown LocalizedException in PHPDocs of register and setQty methods.

Fixed Issues

1. Incorrect phpdoc should be Shipment\Item not Invoice\Item #13992: Incorrect phpdoc should be Shipment\Item not Invoice\Item

Manual testing scenarios

1. This is not necessary, this just resolves warnings in the IDE.

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-engcom-team]

Hi @chirag-wagento. Thank you for your contribution
Here is some useful tips how you can test your changes using Magento test environment.
Add the comment under your pull request to deploy test or vanilla Magento instance:

• @magento-engcom-team give me test instance - deploy test instance based on PR changes
• @magento-engcom-team give me {$VERSION} instance - deploy vanilla Magento instance

For more details, please, review the Magento Contributor Assistant documentation

[chirag-wagento]

As per this tickets comment #16122 (comment) created new pull request.

[orlangur]

Hi @chirag-wagento, when porting pull requests author of the original commit must be preserved: ab64a2c

Please cherry-pick this commit into your branch instead of doing a new commit from scratch and force push into the same branch.

[orlangur]

Closing due to inactivity. Feel free to reach me out anytime later if you wish to continue work on this pull request and it will be reopened.