deps: update dependency absl-py to v2.1.0 (#2659)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [absl-py](https://togithub.com/abseil/abseil-py) | `==2.0.0` -> `==2.1.0` | [![age](https://developer.mend.io/api/mc/badges/age/pypi/absl-py/2.1.0?slim=true)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://developer.mend.io/api/mc/badges/adoption/pypi/absl-py/2.1.0?slim=true)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://developer.mend.io/api/mc/badges/compatibility/pypi/absl-py/2.0.0/2.1.0?slim=true)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://developer.mend.io/api/mc/badges/confidence/pypi/absl-py/2.0.0/2.1.0?slim=true)](https://docs.renovatebot.com/merge-confidence/) |

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### Release Notes

<details>
<summary>abseil/abseil-py (absl-py)</summary>

### [`v2.1.0`](https://togithub.com/abseil/abseil-py/blob/HEAD/CHANGELOG.md#210-2024-01-16)

[Compare Source](https://togithub.com/abseil/abseil-py/compare/v2.0.0...v2.1.0)

##### Added

-   (flags) Added `absl.flags.override_value` function to provide `FlagHolder`
    with a construct to modify values. The new interface parallels
    `absl.flags.FlagValues.__setattr__` but checks that the provided value
    conforms to the flag's expected type.
-   (testing) Added a new method `absltest.TestCase.assertDataclassEqual` that
    tests equality of `dataclass.dataclass` objects with better error messages
    when the assert fails.

##### Changed

-   (flags) `absl.flags.argparse_flags.ArgumentParser` now correctly inherits
    an empty instance of `FlagValues` to ensure that absl flags, such as
    `--flagfile`, `--undefok` are supported.
-   (testing) Do not exit 5 if tests were skipped on Python 3.12. This follows
    the CPython change[https://togithub.com/python/cpython/pull/113856](https://togithub.com/python/cpython/pull/113856)3856.

##### Fixed

-   (flags) The flag `foo` no longer retains the value `bar` after
    `FLAGS.foo = bar` fails due to a validation error.
-   (testing) Fixed an issue caused by
    [this Python 3.12.1 change](https://togithub.com/python/cpython/pull/109725)
    where the test reporter crashes when all tests are skipped.

</details>

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library_generation/requirements.txt

@@ -1,4 +1,4 @@
-absl-py==2.0.0
+absl-py==2.1.0
 attr==0.3.2
 attrs==23.2.0
 black==24.3.0