Fix federated_settings_identity_provider attribute name (#791)

Co-authored-by: Florent Planque <[email protected]>

Author: florenp

website/docs/r/federated_settings_identity_provider.html.markdown

@@ -48,7 +48,7 @@ In addition to all arguments above, the following attributes are exported:
 
 ### FederatedSettingsIdentityProvider
 
-* `idp_id` - Unique 20-hexadecimal digit string that identifies the IdP.
+* `okta_idp_id` - Unique 20-hexadecimal digit string that identifies the IdP.
 
 ## Import