graphics/py-openimageio: remove BROKEN marker at r535108/2.1.11.2_5

The port builds in poudriere for me, I suppose that the order of events was:

1. the build snapshot the ports tree with a failing and pre-528040 revision
2. antoine@ received pkg-fallout@ and marked the port broken
3. tcberner@ fixed py-openimageio.

(Yes that's "2" twice because the ordering is unknown and also irrelevant)

Poudriere builds succeeded for me for r535108 on 12.1-RELEASE-p4 amd64:
graphics/py-openimageio (py37) 2.1.11.2_5
graphics/py-openimageio@py27 2.1.11.2_5

Since the port inherited the openimageio's PORTREVISION bumps after the
two OpenEXR/ilmbase updates, no further bump necessary.