minor fix to correctly export spans to datasets

[dinmukhamedm]

Spans were exported to datasets into the data field despite having data, target, and metadata keys. This was because target was only visually converted to a JSON object, but remained a string in the state. This commit addresses that

---

[!IMPORTANT] Fixes JSON export issue in ExportSpansDialog by ensuring data and target are correctly initialized as JSON objects.

• Behavior:
  • Fixes issue where data and target were not correctly exported as JSON objects in ExportSpansDialog.
  • Initializes data and target using toJsonObject() to ensure proper JSON conversion.
• Code Simplification:
  • Simplifies JSON stringification in Formatter by using data, target, and metadata state variables directly.

^{This description was created by for c27ecd913b6b4b9edcb6b0b8dd9e5303279e44b3. It will automatically update as commits are pushed.}