Bump external/Catch2 from `6185d0c` to `b56c474` (#1538)

Bumps [external/Catch2](https://github.com/catchorg/Catch2) from `6185d0c` to `b56c474`.
- [Release notes](https://github.com/catchorg/Catch2/releases)
- [Commits](6185d0cc0a...b56c474260)

---
updated-dependencies:
- dependency-name: external/Catch2
  dependency-type: direct:production
...

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Co-authored-by: Alan Jowett <alanjo@microsoft.com>

external/Catch2

@@ -1 +1 @@
-Subproject commit 6185d0cc0a737d5a009f626d3611b868512d12f7
+Subproject commit b56c4742606c2926f5c9cc6ad2b4ce622b888918