This can **never** be the case, therefore this code is redundant, so nuke it.

It is not possible to associate more than one `DimCoord` as the dimensional coordinate of a cube dimension i.e. the `iris.cube.Cube.add_dim_coord()` will only allow you to add **one** `DimCoord` per dimension.

For the case when there is a `DimCoord` associated with a dimension **and** there is a `DimCoord` in the auxiliary coordinate pot associated with the same dimension, `coords = cube.coords(dimensions=dim, dim_coords=True)` will *only ever* return the `DimCoord` from the dimensional coordinate pot.