Vestiges of ``smriprep.workflows.anatomical.init_anat_preproc_wf``

[oesteban]

$ git grep init_anat_preproc_wf
docs/workflows.rst: :func:~smriprep.workflows.anatomical.init_anat_preproc_wf (see below).
docs/workflows.rst: from smriprep.workflows.anatomical import init_anat_preproc_wf
docs/workflows.rst: wf = init_anat_preproc_wf(
docs/workflows.rst::py:func:~smriprep.workflows.anatomical.init_anat_preproc_wf.

It looks like we stopped using smriprep.workflows.anatomical.init_anat_preproc_wf, however, we did not update the documentation accordingly.