Fix the indentation error in quick_qc.py that causes errors generally.

Traceback (most recent call last):
  File "/FastSurfer/FastSurferCNN/run_prediction.py", line 34, in <module>
    from FastSurferCNN.quick_qc import check_volume
  File "/FastSurfer/FastSurferCNN/quick_qc.py", line 70
    sys.exit(0)
              ^
TabError: inconsistent use of tabs and spaces in indentation

FastSurferCNN/quick_qc.py

@@ -67,6 +67,6 @@ def check_volume(aparc_aseg_segfile, voxvol, thres=0.75):
 
     if not check_volume(inseg_data, inseg_voxvol):
         print('WARNING: Total segmentation volume is very small. Segmentation may be corrupted! Please check.')
-    	sys.exit(0)
+        sys.exit(0)
     else:
         sys.exit(0)