chromite: python3 super() change

super() instead of super(cls, self)

BUG=none
TEST=CQ

Change-Id: I053583b8cf014a9ce6cd1dab86de88720df81660
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/3054981
Tested-by: Jae Hoon Kim <kimjae@chromium.org>
Commit-Queue: Jae Hoon Kim <kimjae@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/cli/flash.py b/cli/flash.py
index e6ebff1..3213806 100644
--- a/cli/flash.py
+++ b/cli/flash.py
@@ -37,7 +37,7 @@
   """Progress bar for flashing image to operation."""
 
   def __init__(self, image):
-    super(UsbImagerOperation, self).__init__()
+    super().__init__()
     self._size = os.path.getsize(image)
     self._transferred = 0
     self._bytes = re.compile(r'(\d+) bytes')