Bump vant from 1.6.28 to 2.2.14 in /mobile-web

Bumps [vant](https://github.com/youzan/vant) from 1.6.28 to 2.2.14.
- [Release notes](https://github.com/youzan/vant/releases)
- [Commits](https://github.com/youzan/vant/compare/v1.6.28...v2.2.14)

Signed-off-by: dependabot[bot] <support@github.com>

mobile-web/package.json

@@ -12,7 +12,7 @@
     "axios": "^0.18.0",
     "moment": "^2.24.0",
     "pingpp-js": "^2.2.13",
-    "vant": "^1.3.1",
+    "vant": "^2.2.14",
     "vue": "^2.5.17",
     "vue-router": "^3.0.1",
     "vuex": "^3.1.0"