Towards googleapis/librarian#2456

This PR updates the SHA for the librarian language image to match the
one
[here](https://github.com/googleapis/google-cloud-python/blob/2feb74032fd9c5cc7eaf6072ab03e9e8397bd434/.librarian/state.yaml#L1C1-L1C170).

Owlbot related files are also cleaned up

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Co-authored-by: ohmayr <omairn@google.com>

Thank you for opening a Pull Request! Before submitting your PR, there
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- [ ] Make sure to open an issue as a
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- [ ] Ensure the tests and linter pass
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- [ ] Appropriate docs were updated (if necessary)

Fixes #<issue_number_goes_here> 🦕

PR created by the Librarian CLI to initialize a release. Merging this PR
will auto trigger a release.

Librarian Version: v0.6.0
Language Image:
us-central1-docker.pkg.dev/cloud-sdk-librarian-prod/images-prod/python-librarian-generator@sha256:c8612d3fffb3f6a32353b2d1abd16b61e87811866f7ec9d65b59b02eb452a620
<details><summary>pandas-gbq: 0.31.0</summary>

##
[0.31.0](v0.30.0...v0.31.0)
(2025-11-17)

### Features

* add pandas_gbq.sample (#983)
([ac771c1](ac771c12))

</details>

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Co-authored-by: Anthonios Partheniou <partheniou@google.com>