Explicit Color OCIO role comment fix.

This is an update to the correct OCIO role.

It changes `SceneReference` to `scene_linear`

See https://opencolorio.readthedocs.io/en/latest/guides/authoring/overview.html#config-roles

>     - reference - the color space against which the other color spaces are defined
>NOTE: The reference role has sometimes been misinterpreted as being the space in which “reference art” is stored in.
>
>    - scene_linear - the scene-referred linear-to-light color space, often the same as the reference space

The current OCIO UX working group doc says:

>reference: This role has had multiple interpreted meanings over the years and is a common point of confusion. It is kept in OCIO for backwards compatibility, but the recommendation is that it is not used by apps.

Reviewed By: jbakker

Differential Revision: https://developer.blender.org/D11398

source/blender/blenlib/BLI_color.hh

@@ -86,7 +86,7 @@ std::ostream &operator<<(std::ostream &stream, const eAlpha &space);
 enum class eSpace {
   /** Blender theme color space (sRGB). */
   Theme,
-  /** Blender internal scene linear color space (maps to SceneReference role in OCIO). */
+  /** Blender internal scene linear color space (maps to scene_linear role in OCIO). */
   SceneLinear,
   /** Blender internal scene linear color space compressed to be stored in 4 uint8_t. */
   SceneLinearByteEncoded,