Added from __future__ import annotations to safe_import.py to support python 3.9 (#1642)

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> [!IMPORTANT]
> Added `from __future__ import annotations` to `safe_import.py` for
Python 3.9 compatibility.
> 
>   - **Compatibility**:
> - Added `from __future__ import annotations` to `safe_import.py` to
support Python 3.9 type hinting.
> 
> <sup>This description was created by </sup>[<img alt="Ellipsis"
src="https://img.shields.io/badge/Ellipsis-blue?color=175173">](https://www.ellipsis.dev?ref=BoundaryML%2Fbaml&utm_source=github&utm_medium=referral)<sup>
for 4d80ff5. It will automatically
update as commits are pushed.</sup>

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Author: hellovai

engine/language_client_python/python_src/baml_py/safe_import.py

@@ -1,3 +1,4 @@
+from __future__ import annotations
 from typing import Optional, Type
 from .baml_py import get_version