[bugfix][forms] Remove spurious NonAffineFamiliy tag

When (test|trial)Function(basis, treePathArgs...) with individual path digit arguments, the NonAffineFamiliy was always added. While this does not result in incorrect code, it needlesly deactivates caching accross different elements if this particular syntax was used.

Notice that the other overloads with a singe TreePath object, no tree path at all, or a SubspaceBasis where not affected by this.