ci: add check for PR titles with specific phrases

[devin-ai-integration]

This PR ensures that 'do not merge' will fail the semantic PR title check, as requested by AJ (Aaron ("AJ") Steers (@aaronsteers)).

Link to Devin run: https://app.devin.ai/sessions/22d594d5691648538cf7de8ecfc32c93

[devin-ai-integration]

🤖 Devin AI Engineer

Original prompt from Aaron:

@Devin - Can you copy over the check for "do not merge" in PR titles, from the CDK repo over to the PyAirbyte repo and the main airbyte repo and the morph repo?

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add "(aside)" to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment and CI monitoring