Show collapse icon in Problems panel

src/vs/workbench/contrib/markers/browser/markersPanel.ts

@@ -117,7 +117,7 @@ export class MarkersPanel extends Panel implements IMarkerFilterController {
 		this.rangeHighlightDecorations = this._register(this.instantiationService.createInstance(RangeHighlightDecorations));
 
 		// actions
-		this.collapseAllAction = this._register(new Action('vs.tree.collapse', localize('collapseAll', "Collapse All"), 'monaco-tree-action collapse-all', true, async () => this.collapseAll()));
+		this.collapseAllAction = this._register(new Action('vs.tree.collapse', localize('collapseAll', "Collapse All"), 'monaco-tree-action codicon-collapse-all', true, async () => this.collapseAll()));
 		this.filterAction = this._register(this.instantiationService.createInstance(MarkersFilterAction, { filterText: this.panelState['filter'] || '', filterHistory: this.panelState['filterHistory'] || [], useFilesExclude: !!this.panelState['useFilesExclude'] }));
 	}