fix(openresponses): do not omit required field ORItemParam.Arguments (mudler#9074)

See mudler#9047
Signed-off-by: localai-bot <bot@localai.com>

Signed-off-by: localai-bot <bot@localai.com>

Author: tv42

core/schema/openresponses.go

@@ -96,7 +96,7 @@ type ORItemParam struct {
 	// Function call fields
 	CallID    string `json:"call_id,omitempty"`
 	Name      string `json:"name,omitempty"`
-	Arguments string `json:"arguments,omitempty"`
+	Arguments string `json:"arguments"`
 
 	// Function call output fields
 	Output interface{} `json:"output,omitempty"` // string or []ORContentPart