[Port 2.3] Fixing annotations for some methods.

[tiagosampaio]

Original PR: #16899

Simple changes to annotations by adding throws, etc.

Description

Fixed Issues (if relevant)

No.

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 @tiagosampaio. 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:

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• @magento-engcom-team give me {$VERSION} instance - deploy vanilla Magento instance

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[magento-engcom-team]

Hi @tiagosampaio. Thank you for your contribution.
We will aim to release these changes as part of 2.3.0.
Please check the release notes for final confirmation.