fix optinal byok display name label (#158)

Author: xinyi-gong

com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/preferences/messages.properties

@@ -19,7 +19,7 @@ preferences_page_byok_addModel_dialog_title=Add %s Models
 preferences_page_byok_addModel_modelId=Model ID: *
 preferences_page_byok_addModel_deploymentUrl=Deployment URL: *
 preferences_page_byok_addModel_apiKey=API Key: *
-preferences_page_byok_addModel_displayName=Display Name: *
+preferences_page_byok_addModel_displayName=Display Name:
 preferences_page_byok_addModel_supportVision=Support Vision
 preferences_page_byok_addModel_supportToolCalling=Support Tool Calling
 preferences_page_byok_changeApi_dialog_title=Change %s API Key?