fix(collapse): defaultExpandedNames doesn't work in accrodion mode (#351)

CHANGELOG.en-US.md

@@ -2,6 +2,8 @@
 
 ## Pending
 
+- Fix `n-collapse` the props of defaultExpandedNames does not work, closes [#350](https://github.com/TuSimple/naive-ui/issues/350).
+
 ### Breaking Changes
 
 - `n-select` add `render-tag` prop.

CHANGELOG.zh-CN.md

@@ -2,6 +2,8 @@
 
 ## Pending
 
+- 修复 `n-collapse` 默认指定展开属性无效，关闭 [#350](https://github.com/TuSimple/naive-ui/issues/350)
+
 ### Breaking Changes
 
 - `n-select` 新增 `render-tag` 属性

src/collapse/src/CollapseItem.tsx

@@ -49,6 +49,9 @@ export default defineComponent({
         return !~expandedNames.findIndex(
           (expandedName) => expandedName === name
         )
+      } else if (expandedNames) {
+        const { value: name } = mergedNameRef
+        return name !== expandedNames
       }
       return true
     })