Update provider.md

Corrected the Callback URL since we encountered this when implementing.  Also removed the scopes config item - including this resulted in errors for us.

I had submitted a PR before, and I addressed two feedback items - one was wording and the other was a request to include the optional configurations in the instructions.  Both are addressed.  Apologize I had to make a new PR because I had issues with the other being open so long and I didn't rebase it correctly - better to start fresh.

Signed-off-by: jolies93 <64967243+jolies93@users.noreply.github.com>

docs/auth/atlassian/provider.md

@@ -28,7 +28,7 @@ Name your integration and click on the `Create` button.
 
 Settings for local development:
 
-- Callback URL: `http://localhost:7007/api/auth/atlassian`
+- Callback URL: `http://localhost:7007/api/auth/atlassian/handler/frame`
 - Use rotating refresh tokens
 - For permissions, you **must** enable `View user profile` for the currently
   logged-in user, under `User identity API`
@@ -46,18 +46,24 @@ auth:
       development:
         clientId: ${AUTH_ATLASSIAN_CLIENT_ID}
         clientSecret: ${AUTH_ATLASSIAN_CLIENT_SECRET}
-        scope: ${AUTH_ATLASSIAN_SCOPES}
+        audience: "https://api.atlassian.com"
+        callbackUrl: "https://backstage.example.com/api/auth/atlassian/handler/frame"
+        additionalScopes:
+          - "read:jira-user"
+          - "read:jira-work"
         signIn:
           resolvers:
             # See https://backstage.io/docs/auth/atlassian/provider#resolvers for more resolvers
             - resolver: usernameMatchingUserEntityName
 ```
 
-The Atlassian provider is a structure with three configuration keys:
+The Atlassian provider is a structure with the following configuration keys:
 
 - `clientId`: The Key you generated in the developer console.
 - `clientSecret`: The Secret tied to the generated Key.
-- `scope`: List of scopes the app has permissions for, separated by spaces.
+- `audience`: (Optional) Specifies the intended recipient of the tokens.
+- `callbackUrl`: (Optional) Must match the redirect URL set in Atlassian OAuth settings.
+- `additionalScopes` : (Optional) Additional permissions requested from Atlassian.
 
 **NOTE:** the scopes `offline_access`, `read:jira-work`, and `read:jira-user` are provided by default.