Add STCurrency.h to xrpl_core to fix clio build

[gregtatcam]

High Level Overview of Change

Fixes clio build.

Context of Change

Adds STCurrency.h to RippledCore.cmake.

Type of Change

• [x] 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)
• [ ] Refactor (non-breaking change that only restructures code)
• [ ] Performance (increase or change in throughput and/or latency)
• [ ] Tests (you added tests for code that already exists, or your new feature included in this PR)
• [ ] Documentation update
• [ ] Chore (no impact to binary, e.g. .gitignore, formatting, dropping support for older tooling)
• [ ] Release

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 61.65%. Comparing base (22b7518) to head (650245d).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #4939 +/- ## ======================================== Coverage 61.65% 61.65% ======================================== Files 806 806 Lines 70967 70967 Branches 36690 36690 ======================================== Hits 43752 43752 + Misses 19856 19855 -1 - Partials 7359 7360 +1 ```

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[legleux]

Looks good to me in terms of fixing Clio 👍

@thejohnfreeman @legleux you mentioned something more needed to be done I believe?

Just that I had a PR that moved a bunch of of headers so I'd just add this with that PR #4940.