fix(Dialog): attach should work when showInAttachedElement is true

Author: uyarn

src/dialog/_example/attach.vue

@@ -49,6 +49,7 @@
     <t-dialog
       :visible.sync="visibleShowInAttachedElement"
       header="对话框仅展示在挂载元素区域"
+      attach=".dialog-attach-wrap"
       :showInAttachedElement="true"
       placement="center"
       :onConfirm="() => (this.visibleShowInAttachedElement = false)"

src/dialog/dialog.tsx

@@ -153,7 +153,7 @@ export default mixins(
       return !this.isFullScreen ? { width: getCSSValue(this.width), ...this.dialogStyle } : { ...this.dialogStyle }; // width全屏模式不生效;
     },
     computedAttach(): AttachNode {
-      return this.showInAttachedElement || this.isNormal ? undefined : this.attach || this.globalAttach();
+      return this.isNormal ? undefined : this.attach || this.globalAttach();
     },
   },