hello-world: update to most recent canonical specification

[wolf99]

Recently a .meta/tests.toml file was introduced to each exercise on this track.
The purpose being to show how an exercise aligns (or does not align) to the exercise's canonical-data.json (in the problem-specifications repo), by comparing the UUID assigned to each test case.

See the canonical-data-syncer for how to check the exercises for this.

This has shown that the hello-world exercise has missing or out of date tests.

The request for this issue is to assign the issue to yourself and then (having read our CONTIBUTING.md) update the exercise such that:

• Existing test names are correct
• Existing tests match the requirements of the related canonical-data.json
• Missing tests are added
  • If needed, the example implementation is adjusted to fulfill the added test cases
• Update the related tests.toml file to add the UUIDs that correspond to the updated tests

See the following past PR for an example #493