BREAKING CHANGE: Remove data from FinalResult (#2443)

Author: Kludex

docs/changelog.md

@@ -16,6 +16,8 @@ Pydantic AI is still pre-version 1, so breaking changes will occur, however:
 
 See [#2440](https://github.com/pydantic/pydantic-ai/pull/2440) - The `next` method was removed from the `Graph` class. Use `async with graph.iter(...) as run:  run.next()` instead.
 
+See [#2443](https://github.com/pydantic/pydantic-ai/pull/2443) - The `data` property was removed from the `FinalResult` class. Use `output` instead.
+
 ### v0.5.0 (2025-08-04)
 
 See [#2388](https://github.com/pydantic/pydantic-ai/pull/2388) - The `source` field of an `EvaluationResult` is now of type `EvaluatorSpec` rather than the actual source `Evaluator` instance, to help with serialization/deserialization.

pydantic_ai_slim/pydantic_ai/result.py

@@ -507,11 +507,6 @@ class FinalResult(Generic[OutputDataT]):
     tool_call_id: str | None = None
     """ID of the tool call that produced the final output; `None` if the output came from unstructured text content."""
 
-    @property
-    @deprecated('`data` is deprecated, use `output` instead.')
-    def data(self) -> OutputDataT:
-        return self.output
-
     __repr__ = _utils.dataclasses_no_defaults_repr