for testing purposes

[parthea]

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
• Ensure the tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

Fixes #<issue_number_goes_here> 🦕

[gemini-code-assist]

Code Review

This pull request updates the minimum supported version of google-api-core to 2.28.0 across various post-processing configurations and constraints. It introduces a compatibility module _compat.py in google-ads-admanager to handle older versions of google-api-core gracefully, and refactors all REST transports to utilize a centralized transcode_request helper, significantly reducing boilerplate code in the generated transport classes. Additionally, manual Python and dependency version checks in __init__.py have been replaced with direct calls to api_core. There are no review comments to assess, so I have no further feedback to provide.