build(json-schema): update version to remove high-severity (#721)

## Summary
Updated the version of the lib json-schema

There is a vulnerability which was fixed in version 0.4.0 

Prototype Pollution  https://snyk.io/vuln/SNYK-JS-JSONSCHEMA-1920922

Author: makiri1993

packages/optimizely-sdk/package-lock.json

@@ -45,7 +45,7 @@
     "@optimizely/js-sdk-event-processor": "^0.9.2",
     "@optimizely/js-sdk-logging": "^0.3.1",
     "@optimizely/js-sdk-utils": "^0.4.0",
-    "json-schema": "^0.2.3",
+    "json-schema": "^0.4.0",
     "murmurhash": "0.0.2"
   },
   "devDependencies": {