fix: submitting persisting true state

[Karadjordje]

This issue is connected with this PR https://github.com/final-form/react-final-form/pull/513/files

When onSubmit returns without delay update batches and re-render never happens.

This will fix issue with subscription and submitting where submitting will stay true even thought the updated value should be false

Closes #875, #903

[codesandbox-ci[bot]]

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Sandbox	Source
React Final Form - Simple Example	Configuration
React Final Form - Synchronous Record Level Validation	Configuration
React Final Form - Synchronous Field Level Validation	Configuration
React Final Form - Submission Errors	Configuration
final-form/react-final-form	Configuration

[gertdreyer]

Also closes final-form/final-form#412