fix concatenate tests failing due to not being bit exact

Since requantize is now offloaded, concatenate tests were failing
due a reference not being used.

Change-Id: I44b26b5daecfefb776ca19e6646f3690f5570f52

Author: lhutton1

tests/python/contrib/test_ethosu/test_codegen.py

@@ -950,7 +950,10 @@ def concat_func(*inputs):
         op = tf.concat(list(inputs), axis)
         return op
 
-    _compare_tvm_with_tflite(concat_func, shapes, accel_type)
+    # TODO(lhutton1) For now output is not bit exact with TFLite.
+    # This is because TFLite reference kernels are not being used.
+    # For this, TFLite will need upgrading to 2.6.
+    _compare_tvm_with_tflite(concat_func, shapes, accel_type, output_tolerance=1)
 
 
 @pytest.mark.parametrize("accel_type", ACCEL_TYPES)