Exclude metainternal from C++ API snapshots (#56545)

Summary:
Pull Request resolved: #56545

Add */metainternal/* to top-level exclude_patterns in the C++ API snapshot config.
This directory may contain internal headers that are not part of the public React Native
C++ API surface.

Changelog: [Internal]

Reviewed By: cortinico

Differential Revision: D101879633

fbshipit-source-id: a0118c146ba6eca667671bd572cd39c59e339469

Author: lavenzg

scripts/cxx-api/config.yml

@@ -6,6 +6,7 @@ exclude_patterns:
   - "*/test/*"
   - "*/test_helper/*"
   - "*/stubs/*"
+  - "*/metainternal/*"
 
 exclude_symbols:
   - "Fantom"