refactor(TerrainViewer): remove unused isAutoRotating state

删除了未使用的isAutoRotating响应式状态变量，清理冗余代码

src/components/TerrainViewer.vue

@@ -23,7 +23,6 @@ const loading = ref(true)
 const error = ref(null)
 const veModel = ref(props.verticalExaggeration)
 const infoText = ref('')
-const isAutoRotating = ref(false)
 const realtimeMetrics = ref([])
 const loadingMetrics = ref(false)