Fix header rerender bug which occurs when a table has two header rows…

… updated simultaneously.

This is a proposed solution to https://github.com/angular/angular/issues/58347.

src/cdk/table/table.ts

@@ -1084,7 +1084,10 @@ export class CdkTable<T>
    * re-render that section.
    */
   private _renderUpdatedColumns(): boolean {
-    const columnsDiffReducer = (acc: boolean, def: BaseRowDef) => acc || !!def.getColumnsDiff();
+    const columnsDiffReducer = (acc: boolean, def: BaseRowDef) => {
+      const diff = !!def.getColumnsDiff();
+      return acc || diff;
+    }
 
     // Force re-render data rows if the list of column definitions have changed.
     const dataColumnsChanged = this._rowDefs.reduce(columnsDiffReducer, false);