Force UVW column to be fixed shape to ensure compatibility with StandardStMan input MS
Dp3 was crashing when using an input ms with a storage manage of StandardStMan gibving the error: std exception detected: Table DataManager error: TiledStMan: TiledColumnStMan needs array column UVW to be FixedShape
Since the UVWs have always a fixed shape, a line is added to enforce that in the MSWriter even if the input allows varying shape.