Remove macbeth chart watermark

[DevTGHa]

Remove Macbeth chart watermark

Summary

The watermark added on Macbeth chart was causing MacBethSample._sample_patch failure.

During analyse process, OpenVPCal process kept raising error:

Lib\site-packages\numpy\_core\fromnumeric.py:3860: RuntimeWarning: Mean of empty slice.

This was coming from the call chain:

1. main_window.py: run_analyse() calls self.analyse(led_walls)
2. application_base.py: analyse() creates Processing object and calls
   processing.run_sampling()
3. sample_patch.py: MacBethSample._sample_patch() calls np.mean(np.array(samples), axis=0)

After further investigation, I found that the watermark was causing detect_colour_checkers_segmentation failure. Please see the reference image bellow that was generated by detect_colour_checkers_segmentation(show=True).

Reference 1

Reference 2

Old Macbeth Chart without watermark

OpenVPCal\tests\test_open_vp_cal\resources\RED_WhiteBalance_Test

[DevTGHa]

@davisadam10 I was wondering if you are happy to have this change?
If so, I can try to update the test to reflect removed watermark from the Macbeth chart.