fix(module:date-picker): fix code comment (#7991)

Author: cxb1021

components/date-picker/date-picker.component.ts

@@ -654,7 +654,7 @@ export class NzDatePickerComponent implements OnInit, OnChanges, AfterViewInit,
         return this.close();
       }
 
-      // check if the value has change for a simple datepicker, let us to avoid notify the control for nothing
+      // check if the value has change for a range picker, let us to avoid notify the control for nothing
       if (this.isRange) {
         const [previousStartDate, previousEndDate] = datePickerPreviousValue as CandyDate[];
         const [currentStartDate, currentEndDate] = value as CandyDate[];