Update PSA services documentation (#777)

* update PSA doc

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Co-authored-by: Mohamed BOUSSAA <mohamed.boussaa@activeeon.com>

src/docs/PSA/references/Service_Execution.adoc

@@ -2,5 +2,5 @@ PSA services can be instantiated in two different ways:
 
 1- Via the <<_psa_portal,ProActive Service Automation>> (PSA) Portal.
 
-2- Via standard workflows (also called *Management Workflows*). ProActive includes predefined standard workflows that manage PSA service lifecycles (e.g., launch and stop PSA services).
-These workflows are provided in the bucket *Service_Automation* under the project *Service Automation - Management*. Their names are constructed using the pattern *PSA_Service_Name* followed by the suffix *_Service*.
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+2- Via Workflow Execution Portal. To launch PSA services, you have to open the Submit Window in the Workflow Execution Portal and then select 'Service Workflows Only' option to filter PSA services from the list of workflows.
+After selecting a PSA service to submit, you can provide variable values that help configure this service then press submit.
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