fix(github): Correct instructions on GHE docs (#13875)

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## DESCRIBE YOUR PR
My change from #13393 were
a bit overzealous. I think it used to be possible to be a GHE Cloud
customer but self-hosted and managed via GitHub, in an on-premise type
situation. Most GHE Cloud customers should _not_ be using the enterprise
integration, as the hosted app will be much easier. Added verbiage to
clarify the only thing we care about is the base URL and app
credentials.

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Author: leeandher

docs/organization/integrations/source-code-mgmt/github/index.mdx

@@ -5,13 +5,12 @@ description: "Learn more about Sentry's GitHub integration and how it can track
 ---
 
 There are two types of GitHub integrations, so make sure you're choosing the correct one:
-- [GitHub](#installing-github) - For regular GitHub accounts, these will have URLs like `https://github.com/org-name`. Follow the '[Installing GitHub](#installing-github)' instructions, **do not use the GitHub Enterprise integration**.
-- [GitHub Enterprise](#installing-github-enterprise) - For GitHub Enterprise Cloud or GitHub Enterprise Server instances. Some example URLs:
-  - `https://github.org-name.com`
-  - `https://github.com/enterprises/org-name`
-  - `https://org-name.ghe.com/`
+- [GitHub](#installing-github) - For most GitHub accounts, these will have URLs like `https://github.com/org-name`. **Most Github Enterprise Cloud customers should be able to use this integration. **Follow the '[Installing GitHub](#installing-github)' instructions, **do not use the GitHub Enterprise integration and please begin the installation from Sentry**.
+- [GitHub Enterprise](#installing-github-enterprise) - For GitHub Enterprise instances that **cannot be accessed from `https://github.com`**. For example, a custom domain:
+  - `https://github.example.com`
+  - `https://ghe.example.com/`
 
-  These [can also be modified](https://docs.github.com/en/enterprise-cloud@latest/admin/managing-your-enterprise-account/changing-the-url-for-your-enterprise) so make sure you have have the correct URL during installation. For these accounts, follow the '[Installing GitHub Enterprise](#installing-github-enterprise)' instructions, **do not use the regular GitHub integration**.
+ For these accounts, and if your organization cannot access the [Sentry's GitHub App](https://github.com/apps/sentry-io) for whatever reason, follow the '[Installing GitHub Enterprise](#installing-github-enterprise)' instructions; it'll guide you through making your own GitHub App and allowing Sentry to use it for access to your organization. **Do not use the regular GitHub integration**.
 
 ## Installing GitHub