fix: ensure Wrapper.setSelected() idempotency

Author: vvanpo

Diff for: packages/test-utils/src/wrapper.js

@@ -404,6 +404,10 @@ export default class Wrapper implements BaseWrapper {
     }
 
     if (tagName === 'OPTION') {
+      if (this.element.selected) {
+        return
+      }
+
       // $FlowIgnore
       this.element.selected = true
       // $FlowIgnore