Handle repositories that don't support draft PRs

[codegen-sh]

Description

This PR addresses the issue described in CG-11610 by implementing a fallback mechanism for repositories that don't support draft PRs.

Changes

• Modified the create_pull method in GitRepoClient to:
  • First attempt to create a draft PR when requested
  • Catch GitHub exceptions with status code 422 that mention "draft" in the error message
  • Fall back to creating a regular PR when draft PRs aren't supported
  • Log appropriate warning messages

Testing

The implementation has been tested with:

• Repositories that support draft PRs (normal behavior)
• Repositories that don't support draft PRs (falls back to regular PR)

This change ensures that the PR creation process is more robust and works across all GitHub repositories, including older GitHub Enterprise Server instances that may not support draft PRs.

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