chore: replace the call to setScatteringFactorTableByType

[zmx27]

Problem

As in diffpy/diffpy.srreal#21, the setScatteringFactorTableByType method has been deprecated.

Proposed solution

Remove the setScatteringFactorTableByType method calls and replace them with the new API. For example, use something like

obj.scatteringfactortable = SFTNeutron()