fix: Correct wrong instructions for typescript ejecting

[anyonecancode]

As written, the help text says that a user can run eject-ts to create a standalone server.ts. However, this is incorrect. Doing so simply creates a server.js -- all text following eject is ignored. For instance, one could run eject-foo and get no error and have a server.js generated, even though there is no eject-foo command.

Instead, a user must pass in the lang flag:

fastify-cli/eject.js

Lines 25 to 26 in 426e359

	if (opts.lang === 'ts' || opts.lang === 'typescript') {
	template = 'eject-ts'

The easiest way to update this help test looks to be to use the ts rather than typescript value for --lang, so that it can easily fit into the existing help text format.

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[mcollina]

lgtm