RadioGroup: not produce invalid HTML in table if "is" attribute is specify (#17070)

packages/radio/src/radio-group.vue

 <template>
-  <div
+  <component
+    :is="_elTag"
     class="el-radio-group"
     role="radiogroup"
     @keydown="handleKeydown"
   >
     <slot></slot>
-  </div>
+  </component>
 </template>
 <script>
   import Emitter from 'element-ui/src/mixins/emitter';
@@ -41,6 +42,9 @@
       _elFormItemSize() {
         return (this.elFormItem || {}).elFormItemSize;
       },
+      _elTag() {
+        return (this.$vnode.data || {}).tag || 'div';
+      },
       radioGroupSize() {
         return this.size || this._elFormItemSize || (this.$ELEMENT || {}).size;
       }