Description

Add a section to the GitHub App integration page to clarify that a GH org with the GH App installed can only be integrated with one CircleCI org.

Reasons

Help prevent people getting confused if they do try to integrate with a second org

Please follow our style when contributing to CircleCI docs. Our style guide is here: https://circleci.com/docs/style/style-guide-overview.

Please take a moment to check through the following items when submitting your PR (this is just a guide so will not be relevant for all PRs) 😸:

[ ] Break up walls of text by adding paragraph breaks.
[ ] Consider if the content could benefit from more structure, such as lists or tables, to make it easier to consume.
[ ] Keep the title between 20 and 70 characters.
[ ] Consider whether the content would benefit from more subsections (h2-h6 headings) to make it easier to consume.
[ ] Check all headings h1-h6 are in sentence case (only first letter is capitalized).
[ ] Is there a "Next steps" section at the end of the page giving the reader a clear path to what to read next?
[ ] Include relevant backlinks to other CircleCI docs/pages.