Update the documentation of `CONSTRAINT_DISABLE` and `CONSTRAINT_OFF`
flags to clearly distinguish them from each other.
- `CONSTRAINT_OFF`: The eye icon in the interface. Managed by the user,
maybe indirectly via the animation system or drivers. Maps to both the
`mute` (positive) and `enabled` (negative) properties in RNA.
- `CONSTRAINT_DISABLE`: The red color in the interface that indicates
invalid settings. Set by Blender when a constraint is considered to be
invalid, for example a 'Copy Location' constraint without a target.
Maps to `is_valid` (negative) in RNA.
No functional changes.
799a6ecd24