Update migrating-oauth-apps-to-github-apps.md to include the 'Delete OAuth App' step

[123MwanjeMike]

These changes are to include the 'Delete OAuth App' step in 'Migrating OAuth Apps to GitHub Apps'

Why:

Closes #8067 (comment), #8640

What's being changed:

Adding the 'Delete OAuth App' step

Check off the following:

• I have reviewed my changes in staging (look for the latest deployment event in your pull request's timeline, then click View deployment).
• For content changes, I have completed the self-review checklist.

Writer impact (This section is for GitHub staff members only):

• This pull request impacts the contribution experience
  • I have added the 'writer impact' label
  • I have added a description and/or a video demo of the changes below (e.g. a "before and after video")

---

edited by staff:
Removed square brackets around issue link for automatic issue linking to the PR

[welcome]

Thanks for opening this pull request! A GitHub docs team member should be by to give feedback soon. In the meantime, please check out the contributing guidelines.

[ramyaparimi]

@123MwanjeMike Thanks so much for opening a PR! I'll get this triaged for review ⚡

[skedwards88]

🚀 Thank you for this addition! I am unable to make suggestions or resolve the merge conflict with main for this PR. (Possibly changing the settings described in step 7 here would allow this.) Normally, I would make minor changes to reduce busy work for you, but in this case you will need to make the changes.

To get this PR approved, you will need to:

1. resolve the merge conflict with main
2. use a relative URL

The final two sections would end up looking something like this:

### Encourage users to revoke access to your OAuth app

As your GitHub App installation base grows, consider encouraging your users to revoke access to the legacy OAuth integration. For more information, see "[Authorizing OAuth Apps](/github/authenticating-to-github/keeping-your-account-and-data-secure/authorizing-oauth-apps)."

### Delete the OAuth App

To avoid abuse of the OAuth App's credentials, consider deleting the OAuth App. This action will also revoke all of the OAuth App's remaining authorizations. For more information, see "[Deleting an OAuth App](/developers/apps/managing-oauth-apps/deleting-an-oauth-app)."

[123MwanjeMike]

@skedwards88, thank you for your feedback. Sorry I made the changes from a new branch within the docs repository rather than from my fork and thus you could not the changes as desired.
I have however created a new pull request here from a forked repository with the new changes you proposed.

[123MwanjeMike]

Proposed changes already merged

[ghost]

Ok