PR #25350 - OpenAPITools/openapi-generator

Description

This PR modernizes the Python version requirements and CI configurations for the python-pydantic-v1 generator.

Changes

Update the minimum supported Python version to 3.11 in pyproject.mustache and setup.mustache.
Update GitHub Actions, GitLab CI, and Travis CI configurations to test Python 3.11, 3.12, 3.13, and 3.14.
Remove outdated Python versions from the CI test matrices.
Regenerate the affected samples to reflect the updated templates.

These changes improve consistency between package metadata and CI configurations, reduce maintenance overhead, and align the generator with newer Python versions.

Breaking change: Generated clients will now require Python 3.11 or newer.

Testing

Updated the generated samples to reflect the template changes.
CI validation pending.

PR checklist

Read the [contribution guidelines](https://github.com/openapitools/openapi-generator/blob/master/CONTRIBUTING.md).

Run the following to build the project and update samples:

./mvnw clean package || exit
./bin/generate-samples.sh ./bin/configs/*.yaml || exit
./bin/utils/export_docs_generators.sh || exit

If the PR targets a particular programming language, @mention the [technical committee](https://github.com/openapitools/openapi-generator/#62---openapi-generator-technical-committee) members for review.

Summary by cubic

Raises the minimum supported Python version and updates CI test matrices for the python-pydantic-v1 generator.

Generated clients now require Python 3.11 or newer: the Poetry constraint is >=3.11,<3.15 and setup.py requires >=3.14,<3.15. GitHub Actions, GitLab CI, and Travis CI test matrices now cover Python 3.11 through 3.14 instead of 3.7 through 3.12. The generator's reported language version and docs reflect the new constraints, and the affected samples are regenerated.

Closes #25349.