fix debug UI doesn't cleanup spinners on debug session end

fixes #80402

src/vs/workbench/api/browser/mainThreadDebugService.ts

@@ -378,6 +378,7 @@ class ExtensionHostDebugAdapter extends AbstractDebugAdapter {
 	}
 
 	public stopSession(): Promise<void> {
+		this.cancelPending();
 		return Promise.resolve(this._proxy.$stopDASession(this._handle));
 	}
 }