fix: updated return type of getDialogState in RequestEnvelopeUtils

[Sleepingtree]

Description

Updated getDialogState in RequestEnvelopeUtils to return the correct type of DialogState

Motivation and Context

getDialogState was not auto completing in my local project because it was returning a string and not a DialogState

Testing

Local unit tests all pass, project builds, no linter issues

Screenshots (if appropriate)

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Docs(Add new document content)
• [ ] Translate Docs(Translate document content)

Checklist

• [x] My code follows the code style of this project
• [ ] My change requires a change to the documentation
• [ ] I have updated the documentation accordingly
• [x] I have read the README document
• [ ] I have added tests to cover my changes
• [x] All new and existing tests passed
• [x] My commit message follows Conventional Commit Guideline

License

• [x] By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.