Update and rename about-comparing-branches-in-pull-requests.md to @main

[oicd34]

ROOT LEVEL ZERO

</@>
Thank you for contributing to this project! You must fill out the information below before we can review this pull request. By explaining why you're making a change (or linking to an issue) and what changes you've made, we can triage your pull request to the best possible team for review.
-->

Why:

Closes:

What's being changed (if available, include any code snippets, screenshots, or gifs):

Check off the following:

• A subject matter expert (SME) has reviewed the technical accuracy of the content in this PR. In most cases, the author can be the SME. Open source contributions may require an SME review from GitHub staff.
• The changes in this PR meet the docs fundamentals that are required for all content.
• All CI checks are passing and the changes look good in the review environment.

[github-actions]

How to review these changes 👓

Thank you for your contribution. To review these changes, choose one of the following options:

• Spin up a codespace
• Set up a local development environment

A Hubber will need to deploy your changes internally to review.

Table of review links

Note: Please update the URL for your staging server or codespace.

This pull request contains code changes, so we will not generate a table of review links.

🤖 This comment is automatically generated.