Remove import of non-existent removeIndicatorByIndex from app.js

app.js was trying to import removeIndicatorByIndex which no longer exists in indicators-panel-new.js.
Removed it from the import statement to fix the ES6 module error.

src/api/dashboard/static/js/app.js

@@ -26,8 +26,7 @@ import {
     setActiveIndicators,
     drawIndicatorsOnChart,
     addIndicator,
-    removeIndicatorById,
-    removeIndicatorByIndex
+    removeIndicatorById
 } from './ui/indicators-panel-new.js';
 import { StrategyParams } from './strategies/config.js';
 import { IndicatorRegistry } from './indicators/index.js';