Minor cpu performance fix and typo fix.

deoldify/_device.py

@@ -13,7 +13,7 @@ class _Device:
 
     def is_gpu(self):
         ''' Returns `True` if the current device is GPU, `False` otherwise. '''
-        return self.current() is not DeviceID.CPU
+        return self.current() is not DeviceId.CPU
   
     def current(self):
         return self._current_device
@@ -26,6 +26,5 @@ class _Device:
             import torch
             torch.backends.cudnn.benchmark=False
         
-        os.environ['OMP_NUM_THREADS']='1'
         self._current_device = device    
         return device