Fixed backwards incompatible change to Transport variable event parameters

[gelanivishal]

In PR#15038 the type of event parameter "transport" was incorrectly changed from type DataObject to Array(). This change corrects this back to DataObject.

Fixed Issues (if relevant)

#10210: Transport variable can not be altered in email_invoice_set_template_vars_before Event

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]

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[sidolov]

Hi @gelanivishal , provided changes have been merged with PR #16599.
I'm closing this PR as not relevant.