MINGW: Fix error of use of deleted function

[carlo-bramini]

I tried to build the engine with MinGW and I got several errors like this one:

TheForceEngine/TFE_FileSystem/filewriterAsync.cpp:29:43: error: use of deleted function ‘std::atomic<int>::atomic(const std::atomic<int>&)’
   29 |         std::atomic<s32> s_requestCount = 0;
      |                                           ^
In file included from TheForceEngine/TFE_System/types.h:6,
                 from TheForceEngine/TFE_System/system.h:8,
                 from TheForceEngine/TFE_FileSystem/filewriterAsync.h:2,
                 from TheForceEngine/TFE_FileSystem/filewriterAsync.cpp:1:
/usr/lib/gcc/x86_64-w64-mingw32/14/include/c++/atomic:834:7: note: declared here
  834 |       atomic(const atomic&) = delete;
      |       ^~~~~~
TheForceEngine/TFE_FileSystem/filewriterAsync.cpp:29:43: note: use ‘-fdiagnostics-all-candidates’ to display considered candidates
   29 |         std::atomic<s32> s_requestCount = 0;
      |                                           ^
/usr/lib/gcc/x86_64-w64-mingw32/14/include/c++/atomic:838:17: note:   after user-defined conversion: ‘constexpr std::atomic<int>::atomic(__integral_type)’
  838 |       constexpr atomic(__integral_type __i) noexcept : __base_type(__i) { }
      |                 ^~~~~~

Attached patch fixes it.
Actually, this file doesn't seem to be compiled by the Visual Studio project file, so I could not test if this change works there too. However, I have been able to build the engine also with MSVC even after this fix.