Remove unused onFirstRun.js

[Armored-Dragon]

This script seems to no longer be used in a meaningful way, but it does get added to the running scripts when you reload defaults. This script seems to prompt the user to set a name if it detected the client was on it's first run. However this setting gets set to "false" before this script has a change to execute autonomously. This script is also obsoleted by the in-world wizard present in the serverless tutorial.