Update to fmt 12.1.0 (#105)

Summary:
Needed for macOS cibuildwheel builds to work again.

Pull Request resolved: #105

Test Plan: OSS builds still work.

Reviewed By: yoney

Differential Revision: D107121657

Pulled By: alexmalyshev

fbshipit-source-id: cc0a3aea80cbbfa7d3b406c3a44271c66b5e4543

Author: alexmalyshev

CMakeLists.txt

@@ -207,7 +207,7 @@ endif()
 FetchContent_Declare(
   fmt
   GIT_REPOSITORY https://github.com/fmtlib/fmt
-  GIT_TAG 11.2.0 # 2025-May-03
+  GIT_TAG 12.1.0 # 2025-Oct-29
 )
 FetchContent_MakeAvailable(fmt)