[CDP] Corrected configuration (#2465)

Author: mnocon

docs/cdp/cdp_activation/cdp_configuration.md

@@ -27,9 +27,10 @@ ibexa:
                         stream_file:
                             stream_id: 00000000-00000000-00000000-00000000
                 activations:
+                    -
                         client_id: '%env(CDP_ACTIVATION_CLIENT_ID)%'
                         client_secret: '%env(CDP_ACTIVATION_CLIENT_SECRET)%'
-                        segment_group_identifier: ibexa_cdp
+                        segment_group_identifier: example_segment_group_identifier
 ```
 
 - `account_number` - a [number](#account-number) obtained from Accounts settings in [[= product_name_cdp =]] dashboard