fix: superset-frontend/packages/superset-ui-demo/package.json to redu…

…ce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-CROSSSPAWN-8303230

superset-frontend/packages/superset-ui-demo/package.json

@@ -58,7 +58,7 @@
   "devDependencies": {
     "@babel/core": "^7.9.0",
     "babel-loader": "^8.1.0",
-    "chromatic": "^5.4.0",
+    "chromatic": "^6.0.0",
     "fork-ts-checker-webpack-plugin": "^5.0.7",
     "ts-loader": "^7.0.4",
     "typescript": "^4.5.4"