fix: clear stale first-cell classes before recalculating in columns view (T1318812)

Author: Alyar

packages/devextreme/js/__internal/grids/grid_core/views/m_columns_view.ts

@@ -720,6 +720,12 @@ export class ColumnsView extends ColumnStateMixin(modules.View) {
     appendTemplate.render({ content: $row, container: $table });
   }
 
+  private removeFirstCellClasses(): void {
+    const firstCellClass = this.addWidgetPrefix(CLASSES.firstCell);
+
+    this._tableElement?.find(`.${firstCellClass}`).removeClass(firstCellClass);
+  }
+
   protected toggleFirstCellClass(
     $cell: dxElementWrapper | undefined,
     isFirstValue: boolean,
@@ -737,6 +743,8 @@ export class ColumnsView extends ColumnStateMixin(modules.View) {
   protected updateFirstCellClasses(): void {
     const rows = this._getRows();
 
+    this.removeFirstCellClasses();
+
     rows.forEach((row, index) => {
       const rowIndex = row.rowType === 'header' ? index : null;
       const firstColumn = this._columnsController.getFirstColumn(rowIndex);