fix: experimental-flex-dialpad/ui-src/package.json to reduce vulnerab…

…ilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-BRACES-6838727
- https://snyk.io/vuln/SNYK-JS-MICROMATCH-6838728
- https://snyk.io/vuln/SNYK-JS-GLOBPARENT-1016905

experimental-flex-dialpad/ui-src/package.json

@@ -14,7 +14,7 @@
     "react": "16.5.2",
     "react-dom": "16.5.2",
     "react-select": "^3.1.0",
-    "@twilio/flex-plugin-scripts": "6.0.3"
+    "@twilio/flex-plugin-scripts": "6.4.0"
   },
   "devDependencies": {
     "@twilio/flex-ui": "^1",