Iris 15 readout directions incorrect

[AdvancedImagingUTSW]

Shows bidirectional and reverse bidirectional, which should not be supported by the Iris15.

[AdvancedImagingUTSW]

@annie-xd-wang, according to @SJShep, your commit did fix the issue he was having.

I added one more piece of code to initialize what the proper readout directions are Photometric's light-sheet mode:

        self.camera_parameters["supported_readout_directions"] = [
            "Top-to-Bottom",
            "Bottom-to-Top",
        ]

If you are happy, let's proceed with a merge.