CameraITS: Update python3 in commands to run test.

Bug: 237349713

Test: Run scene0 on pixel device.
Change-Id: I4b1c9305d7c91e36e060932320526a975726bedf
diff --git a/apps/CameraITS/tools/run_all_tests.py b/apps/CameraITS/tools/run_all_tests.py
index 3ecc8df..9bf89bd 100755
--- a/apps/CameraITS/tools/run_all_tests.py
+++ b/apps/CameraITS/tools/run_all_tests.py
@@ -518,13 +518,13 @@
         # Handle repeated test
         if 'tests/' in test:
           cmd = [
-              'python',
+              'python3',
               os.path.join(os.environ['CAMERA_ITS_TOP'], test), '-c',
               '%s' % new_yml_file_name
           ]
         else:
           cmd = [
-              'python',
+              'python3',
               os.path.join(os.environ['CAMERA_ITS_TOP'], 'tests', s, test),
               '-c',
               '%s' % new_yml_file_name