Update doc to mention email case sensitivity for Graphql usage (#1263)

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Author: rakeshjosh2003

docs/admin/permissions/api.mdx

@@ -44,7 +44,7 @@ To enable the permissions API, add the following to the [site configuration](/ad
 The `bindID` value specifies how to uniquely identify users when setting permissions:
 
 - `username`: You can [set permissions](#setting-repository-permissions-for-users) for users by specifying their Sourcegraph usernames. Using usernames is **preferred**, as usernames are required to be unique for each user.
-- `email`: You can [set permissions](#setting-repository-permissions-for-users) for users by specifying their email addresses (which must be verified emails associated with their Sourcegraph user account). This method can lead to unexpected results if there are multiple Sourcegraph user accounts with the same verified email address.
+- `email`: You can [set permissions](#setting-repository-permissions-for-users) for users by specifying their email addresses (which must be verified primary emails associated with their Sourcegraph user account). This method can lead to unexpected results if there are multiple Sourcegraph user accounts with the same verified email address. Also, the email address is case-sensitive, so it should be exactly the same as set on the sourcegraph UI.
 
 After you enable the permissions API, you must [set permissions](#setting-repository-permissions-for-users) to allow users to view repositories (site admins bypass all permissions checks and can always view all repositories).