Use typing.Self in automatic_differentiation (drop typing_extensions)

`machine_learning/automatic_differentiation.py` was the only module
importing `Self` from `typing_extensions`, behind a `# noqa: UP035`.
Since the repo requires Python >=3.14, `typing.Self` (added in 3.11)
is always available, so import it from the stdlib and drop the noqa.

### Describe your change:

* [x] Add an algorithm?
* [ ] Fix a bug or typo in an existing algorithm?
* [ ] Add or change doctests? -- Note: Please avoid changing both code and tests in a single pull request.
* [ ] Documentation change?

### Checklist:

* [x] I have read [CONTRIBUTING.md](https://github.com/TheAlgorithms/Python/blob/master/CONTRIBUTING.md).
* [x] This pull request is all my own work -- I have not plagiarized.
* [x] I know that pull requests will not be merged if they fail the automated tests.
* [x] This PR only changes one algorithm file. If not, please split into separate PRs.
* [x] All new Python files are placed inside an existing directory.
* [x] All filenames are in all lowercase characters with no spaces or dashes.
* [x] All functions and variable names follow Python naming conventions.
* [x] All function parameters and return values are annotated with Python type hints.
* [x] All functions have doctests that pass the automated testing.
* [x] All new algorithms include at least one URL that points to Wikipedia or another similar explanation.

Author: priya-sundaram-dev

machine_learning/automatic_differentiation.py

@@ -12,10 +12,9 @@
 from collections import defaultdict
 from enum import Enum
 from types import TracebackType
-from typing import Any
+from typing import Any, Self
 
 import numpy as np
-from typing_extensions import Self  # noqa: UP035
 
 
 class OpType(Enum):