Issue forms: set the "body" field as required

[tomrav]

Why:

Found a mistake in the docs.

What's being changed:

In the documentation for the new "Issue Forms" the body field is marked as optional, it should be required.

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")

[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]

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

[hubwriter]

@tomrav - Many thanks for fixing this. Much appreciated. 👍

[github-actions]

Thanks very much for contributing! Your pull request has been merged 🎉 You should see your changes appear on the site in approximately 24 hours. If you're looking for your next contribution, check out our help wanted issues ⚡