Fix spelling in schema comments

[brendanfalkowski]

Description (*)

Fix spelling.

Original ticket in magento/magento2 repo was closed because GraphQL work is done in this repo:
magento/magento2#19864

Manual testing scenarios (*)

None, affects comments only.

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]

All committers have signed the CLA.

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