Coat and Fuzz parameter order inconsistent between specification and reference implementation

Clearly a very minor detail, but the reference implementation has [Fuzz before Coat](https://github.com/AcademySoftwareFoundation/OpenPBR/blob/main/reference/open_pbr_surface.mtlx#L50) while the specification has [Coat before Fuzz](https://academysoftwarefoundation.github.io/OpenPBR/#parameterreference) in the parameter reference.

Compare the parameter order in reference/open_pbr_surface.mtlx at the linked location with the specification's parameter reference. Make the Coat and Fuzz order consistent between both sources, then verify that the two references show the same ordering.

Written by the indexing model from the issue text.