Fix issue with schema

[AreWeDreaming]

Description

Type of Change

• 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 not work as expected)
• Documentation update
• Code refactoring
• Other (please describe):

Testing

Verified against imas_composer (GA-FDP/imas_composer#92)

Pre-Merge Checklist

• OMFIT has been tested with this OMAS version and you will create a PR on OMFIT that updates the OMAS submodule once this has been merged.
• Version number has been incremented if this is a major modification or important bug fix
  • To increment the version: Edit the version number in omas/version file
  • Follow semantic versioning: MAJOR.MINOR.PATCH (e.g., 0.94.2 → 0.94.3 for bug fixes, 0.94.2 → 0.95.0 for new features)
  • A GitHub release will be automatically created when this PR is merged if the version number has changed

Additional Notes

[torrinba]

Good fix! I will try to remember to check the IMAS schema when reviewing new mappings from now on.

Technically this should be considered a breaking change based on the current state of master, and would only be non-breaking prior to the merge of #429. Since that hasn't made it into any releases yet it seems fine to overlook in this case