fix: upgrade @contentstack/utils from 1.3.16 to 1.3.18

Snyk has created this PR to upgrade @contentstack/utils from 1.3.16 to 1.3.18.

See this package in npm:
@contentstack/utils

See this project in Snyk:
https://app.snyk.io/org/sunil-lakshman/project/c6925ec7-da6d-430a-a674-23c77f22d451?utm_source=github&utm_medium=referral&page=upgrade-pr

Author: snyk-bot

package-lock.json

@@ -100,7 +100,7 @@
     "webpack-node-externals": "^3.0.0"
   },
   "dependencies": {
-    "@contentstack/utils": "^1.3.15",
+    "@contentstack/utils": "^1.3.18",
     "@fetch-mock/jest": "^0.2.10",
     "es6-promise": "^4.2.8",
     "fetch-mock": "^12.2.0",