OpenImageIO v2.5.6.0

Release 2.5.6.0 (Dec 1, 2023) -- compared to 2.5.5.0

• oiiotool: --autocc bugfix and color config inventory cleanup #4060
• idiff: Fix issue when computing perceptual diff #4061 (by Aura Munoz)
• ci: Add tiff-misc reference for slightly changed error messages #4052
• ci: Remove MacOS-11 test #4053
• ci: Test against gcc-13 #4059
• build: Better cmake verbose behavior #4037
• docs: Update INSTALL.md to reflect the latest versions we've tested against #4058
• admin: Fix typo in slack-release-notifier version #4046 #4047
• admin: More relicensing code under Apache 2.0 #4038