Update #include to deprecated fmt header

[kromain]

The <fmt/locale.h> header has been marked as deprecated for a while and has finally been removed in fmt v0.9.0:
fmtlib/fmt@5c7d315

Replace with <fmt/format.h> instead, as recommended in the deprecated header.

The vcpkg build with the benchmark feature (./vcpkg install spdlog[core,benchmark]) is currently broken because of this:

[5/16] /usr/bin/c++ -DSPDLOG_COMPILED_LIB -DSPDLOG_FMT_EXTERNAL -I/workspaces/vcpkg/buildtrees/spdlog/src/v1.10.0-3cbe543323/include -isystem /workspaces/vcpkg/installed/x64-linux/include -fPIC -g -std=c++11 -MD -MT bench/CMakeFiles/bench.dir/bench.cpp.o -MF bench/CMakeFiles/bench.dir/bench.cpp.o.d -o bench/CMakeFiles/bench.dir/bench.cpp.o -c /workspaces/vcpkg/buildtrees/spdlog/src/v1.10.0-3cbe543323/bench/bench.cpp
FAILED: bench/CMakeFiles/bench.dir/bench.cpp.o 
/usr/bin/c++ -DSPDLOG_COMPILED_LIB -DSPDLOG_FMT_EXTERNAL -I/workspaces/vcpkg/buildtrees/spdlog/src/v1.10.0-3cbe543323/include -isystem /workspaces/vcpkg/installed/x64-linux/include -fPIC -g -std=c++11 -MD -MT bench/CMakeFiles/bench.dir/bench.cpp.o -MF bench/CMakeFiles/bench.dir/bench.cpp.o.d -o bench/CMakeFiles/bench.dir/bench.cpp.o -c /workspaces/vcpkg/buildtrees/spdlog/src/v1.10.0-3cbe543323/bench/bench.cpp
/workspaces/vcpkg/buildtrees/spdlog/src/v1.10.0-3cbe543323/bench/bench.cpp:18:14: fatal error: fmt/locale.h: No such file or directory
   18 | #    include <fmt/locale.h>
      |              ^~~~~~~~~~~~~~
compilation terminated.

[gabime]

Thanks @kromain