[Concurrency][Windows] Remove unnecessary includes.

TaskLocal.cpp doesn't need <handleapi.h> or <processthreadsapi.h>, both of
which want <windows.h>, which isn't included any more.

rdar://90776105

stdlib/public/Concurrency/TaskLocal.cpp

@@ -36,8 +36,6 @@
 
 #if defined(_WIN32)
 #include <io.h>
-#include <handleapi.h>
-#include <processthreadsapi.h>
 #endif
 
 using namespace swift;