refactor: simplify workflow service by removing unused commit message handling

[DanielSuhett]

No description provided.

[github-actions]

✨ Flash Code Review

Technical Summary of Pull Request

Purpose: This pull request simplifies the code review workflow by removing unused commit message handling and transitioning to an external action for code review.

Implementation Details:

• .github/workflows/code-review.yml:
  • Removes the steps for setting up Node.js, pnpm, installing dependencies, and building the custom action.
  • Replaces the local action usage (./.) with an external action DanielSuhett/flash@v0.0.30.
  • Removes the auto-approve input parameter.
• src/core/workflow-service.ts:
  • Removes the code responsible for fetching and processing commit messages.
  • Removes the commitMessages parameter from the summarizePullRequest function call.

Potential Impact:

• Reduced complexity: Simplifies the workflow by removing unnecessary steps and code.
• Improved maintainability: Using an external action reduces the maintenance burden of the code review process.
• Faster execution: Removing the commit message processing and local action build steps should speed up the workflow execution.
• Dependency on external action: Introduces a dependency on the DanielSuhett/flash action, which could be a risk if the action is not maintained or has issues.
• Loss of commit message context: The removal of commit message handling might impact the quality of the code review summary if the external action doesn't account for commit messages.