Update widget_toolkit_qr

[DavidDWiser]

Overview

Partially addresses this ticket (Prime-Holding/rx_bloc#768)

Updates widget_toolkit_qr dependencies to support latest rxdart and rx_bloc

Checklist

Implementation

• Implementation matches ticket acceptance criteria and technical notes
• Manually tested against Acceptance Criteria
• UI checked on Android / iOS

Stability

• Checked if changes affect any features and verified affected features work as expected
  - [] Added unit tests for new code and verified existing tests work as expected

Code quality

• Updated CHANGELOG.md, README.md and package versions in pubspec.yaml
• Dependencies are updated to latest versions or new tickets are created if there are breaking changes or deprecations
  - [ ] If an unrelated part of the codebase needs to be updated or refactored, create tickets with proposed changes