fix(BaseExport): Fixed declaration lint issue.

Author: gedinakova

projects/igniteui-angular/src/lib/services/exporter-common/base-export-service.ts

@@ -1343,10 +1343,10 @@ export abstract class IgxBaseExporter {
     }
 
     private groupByKeys(items: any[], keys: any[]): any {
-        const group = (data: any[], keys: any[]): any => {
+        const group = (data: any[], currentKeys: any[]): any => {
           if (keys.length === 0) return data;
 
-          const newKeys = [...keys];
+          const newKeys = [...currentKeys];
           const key = newKeys.shift().name;
           const map = new Map<string, any>();