New FCurves for bones were not automatically set to `FCURVE_COLOR_AUTO_RGB`
because the RNA path couldn't be resolved.
That was because the `PointerRNA` passed into the function points to the bone,
but the rna path is relative to the ID.
Fixed by resolving the path from the bones owner ID
Pull Request: https://projects.blender.org/blender/blender/pulls/115517