Remove unnecessary `if data.ndim > 1` in transformers

[fealho]

Problem Description

Many transformers check if the number of dimensions of the input is 1, but the input should always be a Series, so this check should be unnecessary.

Expected behavior

In the transformers, remove any unnecessary lines like the ones below

RDT/rdt/transformers/numerical.py

Line 472 in 5d7f8b7

if data.ndim > 1:

Note: ensure this doesn't break any of our other libraries.