chore: PR template comments out new AEP checklist

[toumorokoshi]

Often, we are making spot fixes to AEPs, and not introducing brand new ones. Therefore, the PR template should comment out new AEP guides rather than requiring it to be removed.

🍱 Types of changes

What types of changes does your code introduce to AEP? Put an x in the boxes
that apply

• Enhancement
• New proposal
• Migrated from google.aip.dev
• Chore / Quick Fix

📋 Your checklist for this pull request

Please review the AEP Style and Guidance for
contributing to this repository.

General

• Basic Guidance is met.
• Ensure that your PR
  references AEPs
  correctly.
• My code has been formatted
  (usually prettier -w .)

💝 Thank you!