[BUG] PSD CMYK to RGB: colors are off

**Describe the bug**
Converting a PSD file to e.g. PNG fails to convert CMYK to RGB correctly.

**To Reproduce**
Steps to reproduce the behavior:
1. Get the .PSD file from the attached archive:
[minimal.zip](https://github.com/OpenImageIO/oiio/files/5904496/minimal.zip)

2. Then simply run `iconvert minimal.psd minimal.png`
3. Then observe that the PNG colors mismatch the correct result of the PSD input

**Expected behavior**
Cyan becomes greenish when converting from CMYK to RGB

**Evidence**
These [lines of code](https://github.com/OpenImageIO/oiio/blob/3e74eae539bcd3662106009baa64ab23a3e48a75/src/psd.imageio/psdinput.cpp#L374) are rather suspicious. Maybe the PSD format is not consistently storing CMYK in a WTF way?

**Platform information:**
- OIIO branch/version: 2.2.10.1 home-brew edition
- OS: macOS

Start in src/psd.imageio/psdinput.cpp around line 374 and reproduce the issue with the attached minimal.zip archive by running `iconvert minimal.psd minimal.png`. Compare the output colors with the PSD input, focusing on the CMYK-to-RGB conversion. Done means cyan converts to the expected greenish RGB result rather than the mismatched PNG colors.

Written by the indexing model from the issue text.