Removed deprecated static-nodes.json file

[rBurgett]

The launch scripts still include the placeholder static-nodes.json file which apparently has been deprecated. The sample data in the file caused errors such as:

ERROR[03-20|08:49:53.246] Node URL <replace with enode://other_public_machine_enode@sentry_machine_ip:30303>: missing 'enr:' prefix for base64-encoded record

When the sample data was removed, the output then said:

Found deprecated node list file static-nodes.json, please use the TOML config file instead

I pulled out the deprecated file and unused environment variable so that the scripts no longer throw those errors. If users want to add static nodes, they can do so in their config.toml with:

[Node.P2P]
StaticNodes = []