[Typing] Clean up invalid python.paddle imports

[ShigureNyako]

PR Category

Environment Adaptation

PR Types

Improvements

Description

This PR cleans up the remaining invalid python.paddle import found on latest develop.

• Replace the type-checking-only import in python/paddle/amp/grad_scaler.py with the public paddle.optimizer.optimizer path.
• Verified no remaining from python.paddle, import python.paddle, or python.paddle. references in the repo.
• Checked that [CodeStyle] Clean up Python 3.10 type-hint diagnostics #79291 is already merged and this PR only touches a different file.

Validation:

• PYTHONPYCACHEPREFIX=/tmp/paddle-clean-python-paddle-imports-pycache python3 -m py_compile python/paddle/amp/grad_scaler.py ✅
• ruff check python/paddle/amp/grad_scaler.py ✅
• pre-commit run --files python/paddle/amp/grad_scaler.py ✅
• git diff --check ✅
• PYTHONPATH=python python3 test/amp/test_grad_scaler_out.py not run successfully: this source checkout does not have a built libpaddle extension, so importing local paddle fails before the test body runs.

是否引起精度变化

否

[ShigureNyako]

已自查：本 PR 只将 TYPE_CHECKING 下残留的 python.paddle 导入替换为公开 paddle 导入路径；本地 py_compile / ruff / pre-commit / git diff --check 均已通过。

@SigureMo 麻烦有空帮忙 review，感谢！

[ShigureNyako]

/re-run all-failed