delete old files and folders in the update procedure
Testing Instructions
install a new 3.3.6 version, update to 3.6.3 and some old files still here:
media/editors/tinymce/plugins/compat3x/editable_selects.js
media/editors/tinymce/plugins/compat3x/form_utils.js
media/editors/tinymce/plugins/compat3x/mctabs.js
media/editors/tinymce/plugins/compat3x/tiny_mce_popup.js
media/editors/tinymce/plugins/compat3x/validate.js
plugins/user/profile/fields/tos.php
Documentation Changes Required
from an 3.3.6 installation, these file no longer exist in Joomla 3.6.3