fix(deps): update dependency vega to v6 [security]

Author: renovate[bot]

docs/package.json

@@ -12,7 +12,7 @@
   },
   "dependencies": {
     "preact": "^10.26.5",
-    "vega": "^5.30.0",
+    "vega": "^6.0.0",
     "vega-lite": "^5.21.0"
   },
   "devDependencies": {

package.json

@@ -103,7 +103,7 @@
     "unknownutil": "3.18.1",
     "valibot": "1.3.1",
     "vality": "6.3.4",
-    "vega": "5.33.0",
+    "vega": "6.2.0",
     "vega-lite": "5.11.0",
     "yup": "1.7.1",
     "zod": "3.25.76",