ci: remove "Auto-Generated Release Notes" header from create-release-pr workflow

[sherwinski]

Description

One Line Summary

Removes the "Auto-Generated Release Notes" header from the create-releases-pr. This helps reserve more space in the release descriptions di

splayed in https://onesignal.github.io/sdk-releases/ for changelog notes.

Details

Motivation

Make it easier for users to see changelog notes at-a-glance on https://onesignal.github.io/sdk-releases/

Scope

Scope is limited to the create-release-pr workflow

Testing

Unit testing

N/A

Manual testing

N/A

Affected code checklist

• Notifications
  • Display
  • Open
  • Push Processing
  • Confirm Deliveries
• Outcomes
• Sessions
• In-App Messaging
• REST API requests
• Public API changes

Checklist

Overview

• I have filled out all REQUIRED sections above
• PR does one thing
  • If it is hard to explain how any codes changes are related to each other then it most likely needs to be more than one PR
• Any Public API changes are explained in the PR details and conform to existing APIs

Testing

• I have included test coverage for these changes, or explained why they are not needed
• All automated tests pass, or I explained why that is not possible
• I have personally tested this on my device, or explained why that is not possible

Final pass

• Code is as readable as possible.
  • Simplify with less code, followed by splitting up code into well named functions and variables, followed by adding comments to the code.
• I have reviewed this PR myself, ensuring it meets each checklist item
  • WIP (Work In Progress) is ok, but explain what is still in progress and what you would like feedback on. Start the PR title with "WIP" to indicate this.

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This change is 

[sherwinski]

@jinliu9508 @abdulraqeeb33 This PR is currently based on main but let me know if there are other branch(es) I should make this change to depending on what is current, beta, etc.

[github-actions]

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[jinliu9508]

Looks good. Basing on main is totally fine.