fix modifier

Author: Tucchhaa

packages/devextreme/js/__internal/scheduler/tooltip_strategies/m_mobile_tooltip_strategy.ts

@@ -64,7 +64,7 @@ const createTabletDeviceConfig = (listHeight) => {
 };
 
 export class MobileTooltipStrategy extends TooltipStrategyBase {
-  public override isDesktop() {
+  protected override isDesktop() {
     return false;
   }
 

packages/devextreme/js/__internal/scheduler/tooltip_strategies/m_tooltip_strategy_base.ts

@@ -144,7 +144,7 @@ export class TooltipStrategyBase {
     }
   }
 
-  public isDesktop(): boolean {
+  protected isDesktop(): boolean {
     return true;
   }