regression fix: nested grids style issue

* while fixing #2110 I broke nested grid styles when manually dragging to sub-nest.

Author: adumesny

doc/CHANGES.md

@@ -82,6 +82,7 @@ Change log
 
 ## 7.2.1-dev (TBD)
 * fix [#2171](https://github.com/gridstack/gridstack.js/issues/2171) `save()` nested grid has extra nested children & options
+* regression for fix #2110: nested grids lost their styles causing wrong rendering when dragging to create sub nesting
 
 ## 7.2.1 (2023-01-14)
 * fix [#2162](https://github.com/gridstack/gridstack.js/pull/2162) removing item from a grid (into another) will now call `change` if anything was also modified during the remove

src/gridstack.ts

@@ -1967,7 +1967,6 @@ export class GridStack {
         Utils.copyPos(node, this._readAttr(this.placeholder)); // placeholder values as moving VERY fast can throw things off #1578
         Utils.removePositioningStyles(el);// @ts-ignore
         this._writeAttr(el, node);
-        el.className = '';
         el.classList.add(gridDefaults.itemClass, this.opts.itemClass);
         this.el.appendChild(el);// @ts-ignore // TODO: now would be ideal time to _removeHelperStyle() overriding floating styles (native only)
         if (subGrid) {