chore: upgrade to newer score-go and go 1.21

[astromechza]

This PR upgrades this repo to the latest commit of score-go score-spec/score-go@562be83 which brings in the generated Go types. This ensures that the repo stays aligned with the fields supported in the official score schema file and that there is a clear source of provenance for the types (the dependency tag should be easier to match to a commit in the score-go repo).

This is functionally a no-op with no resulting changes for any of the test cases.

We also upgrade the required Go version to 1.21 (August 2023).

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• New chore (expected functionality to be implemented)

Checklist:

• My change requires a change to the documentation.
  • I have updated the documentation accordingly.
• I've signed off with an email address that matches the commit author.

[delca85]

👍