Pin to latest twilio-cli-core

Twilio CLI has upgraded to a major version for storing profiles in config files instead of keytars, (Release notes: https://github.com/twilio/twilio-cli-core/releases/tag/6.0.0)

Please verify if anything breaks before merging the PR. Thanks!

Author: onuzbee

package.json

@@ -10,7 +10,7 @@
     "@oclif/config": "^1.13.3",
     "@oclif/plugin-help": "^2.2.3",
     "@twilio-labs/serverless-api": "^4.0.1",
-    "@twilio/cli-core": "^4.3.0",
+    "@twilio/cli-core": "^6.0.0",
     "csv-parse": "^4.8.2",
     "extract-zip": "^1.6.7",
     "ora": "^3.4.0",