Fix compile warning/error on Windows.

sql/threadpool_win.cc

@@ -425,11 +425,6 @@ int TP_pool_win::init()
     }
   }
 
-  /*
-    Control stack size (OS must be Win7 or later)
-  */
-  if (SetThreadpoolStackInformation)
-  {
   TP_POOL_STACK_INFORMATION stackinfo;
   stackinfo.StackCommit = 0;
   stackinfo.StackReserve = (SIZE_T)my_thread_stack_size;
@@ -438,7 +433,6 @@ int TP_pool_win::init()
     tp_log_warning("Can't set threadpool stack size",
       "SetThreadpoolStackInformation");
   }
-  }
   return 0;
 }