(#372) AboutEnumerations: Use Version-Appropriate TryParse() Method

[vexx32]

PR Summary

The overload used is only available in .NET Core; add a branch checking the version to select the appropriate method.

Context

Resolves #372

Changes

• Add a version check so we can pick the appropriate method.
• Add some commentary to explain the choice of method.

Checklist

• Pull Request has a meaningful title.
• Summarised changes.
• Pull Request is ready to merge & is not WIP.
• Added tests / only testable interactively.
  • Make sure you add a new test if old tests do not effectively test the code changed.
• Added documentation / opened issue to track adding documentation at a later date.