Update dependency nuxt to v2.15.6

Author: renovate-bot

package.json

@@ -26,7 +26,7 @@
     "ant-design-vue": "1.7.5",
     "bignumber.js": "9.0.1",
     "core-js": "3.13.0",
-    "nuxt": "2.15.3",
+    "nuxt": "2.15.6",
     "nuxt-client-init-module": "0.3.0",
     "uuid": "8.3.2",
     "vue-lottie": "0.2.1",