Removing default config overriding default value from schema

packages/mermaid/src/defaultConfig.ts

@@ -21,8 +21,8 @@ const config: RequiredDeep<MermaidConfig> = {
   // TODO: Should we replace these with `null` so that they can go in the JSON Schema?
   deterministicIDSeed: undefined,
   elk: {
+    // mergeEdges is needed here to be considered
     mergeEdges: false,
-    nodePlacementStrategy: 'SIMPLE',
   },
   themeCSS: undefined,