style: update

src/app/elements/nav/changeLanWarning.html

 <h1 mat-dialog-title>{{"Warning"|trans}}</h1>
 
-<h2>
+<h3>
   {{"The page will be reload, can you acceptable?"|trans}}
-</h2>
+</h3>
 <div style="float: right">
   <button mat-raised-button (click)="onNoClick()">{{"Cancel"|trans}}</button>
   <button mat-raised-button color="primary" [mat-dialog-close]="selected" cdkFocusInitial>{{"Confirm"|trans}}</button>