chore(deps): Bump Pillow version constraint in google-cloud-documentai-toolbox

[rosston]

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Removals (i.e., breaking changes) for 12.0.0 are documented on Pillow's release.

Fixes #17510 🦕

[gemini-code-assist]

Code Review

This pull request updates the dependency requirements in setup.py for google-cloud-documentai-toolbox by increasing the upper bound of the Pillow library from <12.0.0 to <13.0.0. There are no review comments, and I have no feedback to provide.