magento/graphql-ce#948 - Move preference for ErrorHandlerInterface

[vpodorozh]

Description (#948)

app/etc/graphql/di.xml needs to be removed as well as graphql folder, preference should be added in the app/etc/di.xml file.

Areas are not supported on app level, lib/internal/Magento/Framework/App/Utility/Files.php in used for test only, so such tricks should be avoid.

Caused by #355

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 are green)

[magento-engcom-team]

Hi @novikor, thank you for the review.
ENGCOM-5922 has been created to process this Pull Request
✳️ @novikor, could you please add one of the following labels to the Pull Request?

Label	Description
Auto-Tests: Covered	All changes in Pull Request is covered by auto-tests
Auto-Tests: Not Covered	Changes in Pull Request requires coverage by auto-tests
Auto-Tests: Not Required	Changes in Pull Request does not require coverage by auto-tests

[magento-engcom-team]

Hi @lenaorobei, thank you for the review.
ENGCOM-5922 has been created to process this Pull Request

[ghost]

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