Fix typo on: About Branches page

[thisIsTheFoxe]

fix 1 typo and delete unnecessary space

Why:

Typo. For having nice, grammatically correct docs ^^
No issue or PR found that addresses this.

What's being changed:

The sentence:

The default branch is also the initial branch that Git checks out locally out when someone clones the repository.

and:

GitHub 's

Check off the following:

• All of the tests are passing.
• I have reviewed my changes in staging. (look for the deploy-to-heroku link in your pull request, then click View deployment)

• [n/a] For content changes, I have reviewed the localization checklist
• [n/a] For content changes, I have reviewed the [Content style guide for GitHub Docs (https://github.com/github/docs/blob/main/contributing/content-style-guide.md).

[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.

[janiceilene]

Thanks so much for opening a PR to fix up this article @thisIsTheFoxe! I'll update the branch and get this merged once tests are passing 🍏

[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.

[thisIsTheFoxe]