Fix cache key for asset graph (#17049)

## Summary & Motivation

We should be using the node IDs as part of the cache key, not the keys
of GraphData (which would be the same for every graph)

## How I Tested These Changes

Locally checked that two graphs with no upstream/downstreams had
different graphs

js_modules/dagster-ui/packages/ui-core/src/graph/asyncGraphLayout.ts

@@ -61,7 +61,7 @@ const _assetLayoutCacheKey = (graphData: GraphData) => {
   return JSON.stringify({
     downstream: recreateObjectWithKeysSorted(graphData.downstream),
     upstream: recreateObjectWithKeysSorted(graphData.upstream),
-    nodes: Object.keys(graphData).sort(),
+    nodes: Object.keys(graphData.nodes).sort(),
   });
 };