fix: sqlalchemy dependencies

[wiktorn]

Description

SQLAlchemy v2.0.24 fails with Python 3.13 with error:

AssertionError: Class <class 'sqlalchemy.sql.elements.SQLCoreOperations'> directly inherits TypingOnly but has additional attributes {'__static_attributes__'}.

see bug #11334

Bumping version of SQLAlchemy and fixing Python to version 3.13 to avoid such problems in the future.

Checklist

• I have followed Sample Guidelines from AUTHORING_GUIDE.MD
• README is updated to include all relevant information
• Tests pass: nox -s py-3.9 (see Test Environment Setup)
• Lint pass: nox -s lint (see Test Environment Setup)
• These samples need a new API enabled in testing projects to pass (let us know which ones)
• These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• This sample adds a new Product API, and I updated the Blunderbuss issue/PR auto-assigner with the codeowners for this sample
• Please merge this PR for me once it is approved

[jackwotherspoon]

@wiktorn wouldn't MySQL and SQL Server folders also benefit from this change?

MySQL: https://github.com/GoogleCloudPlatform/python-docs-samples/tree/main/cloud-sql/mysql/sqlalchemy
SQL Server: https://github.com/GoogleCloudPlatform/python-docs-samples/tree/main/cloud-sql/sql-server/sqlalchemy

[wiktorn]

@jackwotherspoon Actually, both MySQL and SQL Server pinned python:3.11 (though different flavors). I aligned Dockerfiles and requirements.txt across these three.