fix: 关联选择支持清空

package.json

 {
   "name": "panda-xform",
-  "version": "4.7.0",
-  "description": "4.7.0 设备选择只读形态",
+  "version": "4.7.1",
+  "description": "4.7.1 关联选择支持清空",
   "keywords": [
     "panda-xform"
   ],

src/core/widgets/select/RelevanceSelect/index.js

@@ -61,6 +61,7 @@ const RelevanceSelect = (props) => {
       onChange={selectChange}
       disabled={disabled}
       placeholder={!disabled ? placeholder : null}
+      allowClear
     >
       {
         options.map((v, i) => <Option value={v.nodeValue} key={i}>{v.nodeValue}</Option>)