opencolorio: add version 2.1.2

[tuccio]

Specify library name and version: opencolorio/2.1.2

New version for the latest release of OpenColorIO,
I didn't change the recipe, I just needed a new patch for some of the files to get the build working.
I can't seem to be able to test using conan-center hooks due to conan-io/hooks#157

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• I've read the guidelines for contributing.
• I've followed the PEP8 style guides for Python code in the recipes.
• I've used the latest Conan client version.
• I've tried at least one configuration locally with the conan-center hook activated.

[CLAassistant]

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[conan-center-bot]

Sorry, the build is only launched for Access Request users. You can request access writing in this issue.