fix: ComboBox readonly state fixed (carbon-design-system#17457)

* fix: combobox readonly state fixed

* fix: removed onfocus event from readonlyhandlers

* fix: removed comments

* fix: removed readonly handler from getmenuprops

---------

Co-authored-by: Preeti Bansal <146315451+preetibansalui@users.noreply.github.com>

packages/react/src/components/ComboBox/ComboBox.tsx

@@ -586,6 +586,12 @@ const ComboBox = forwardRef(
         if (onToggleClick) {
           onToggleClick(event);
         }
+        if (readOnly) {
+          // Prevent the list from opening if readOnly is true
+          event.preventDownshiftDefault = true;
+          event?.persist?.();
+          return;
+        }
 
         if (event.target === textInput.current && isOpen) {
           event.preventDownshiftDefault = true;
@@ -749,6 +755,12 @@ const ComboBox = forwardRef(
               evt.preventDefault();
             }
           },
+          onClick: (evt: MouseEvent<HTMLInputElement>) => {
+            // Prevent the default behavior which would open the list
+            evt.preventDefault();
+            // Focus on the element as per readonly input behavior
+            evt.currentTarget.focus();
+          },
         }
       : {};