[TextInputLayout] Update documentation for setBoxStrokeErrorColor

[p-dmitriy]

Since material 1.8 to change color of cursor in error state inside TextInputLayout we should set strokeErrorColor. Before color was common in error/not error states and comes from colorControlActivated. But documentation of setBoxStrokeErrorColor method still says:

Calling this method when not in outline box mode will do nothing.

Which is no more correct.