Updated Authentication section of README

Signed-off-by: julie-gordon <92888546+julie-gordon@users.noreply.github.com>

Author: julie-gordon

README.md

@@ -13,12 +13,10 @@ For documentation about the file input cloud storage extension, see:
 
 ## Authentication
 This reference implementation supports two [authentication](https://developers.docusign.com/extension-apps/build-an-extension-app/it-infrastructure/authorization/) flows:
-* [Authorization Code Grant](https://developers.docusign.com/extension-apps/build-an-extension-app/it-infrastructure/authorization/#authorization-code-grant) – required for public extension apps
-* [Client Credentials Grant](https://developers.docusign.com/extension-apps/build-an-extension-app/it-infrastructure/authorization/#client-credentials-grant) – available to private extension apps. See [Choosing private distribution instead of public](https://developers.docusign.com/extension-apps/extension-apps-101/choosing-private-distribution/).
+* [Authorization Code Grant](https://developers.docusign.com/extension-apps/build-an-extension-app/it-infrastructure/authorization/#authorization-code-grant) – can be used with both [public and private extension apps](https://developers.docusign.com/extension-apps/extension-apps-101/choosing-private-distribution/) and in all [supported regions](https://developers.docusign.com/extension-apps/extension-apps-101/globalization/).
+* [Client Credentials Grant](https://developers.docusign.com/extension-apps/build-an-extension-app/it-infrastructure/authorization/#client-credentials-grant) – available only with private extension apps that are based in the US.
 
-*Private extension apps can use either authentication method, but public extension apps must use Authorization Code Grant.*
-
-**Note:** In the current release, only Client Credentials Grant is supported.
+**Note:** In the current release, only Client Credentials Grant is supported with file input from cloud storage.
 
 ## Hosted version (no setup required)
 You can use the hosted version of this reference implementation by directly uploading the appropriate manifest file located in the [manifests/hosted/](manifests/hosted) folder to the Docusign Developer Console. See [Upload your manifest and create the extension app](#3-upload-your-manifest-and-create-the-extension-app).
@@ -142,3 +140,4 @@ This type of test shows how the extension functions when invoked from an [extens
 
 
 
+