`usa-label` classes being added to form items.

Problem/Motivation

The CSS class usa-label is being added to form item elements. This class should only be added to the label element of a form item. The usa-label--error CSS class is also being added in the same CSS class array when the element has an error.

Steps to reproduce

1. View the markup of a rendered form with an error
2. See the usa-label and usa-label--error classes on the element with the error.

Proposed resolution

Remove the usa-label and usa-label--error items from the classes array in the uswds_base/templates/form/form-element.html.twig twig template.

Remaining tasks

N/A

User interface changes

None

API changes

None

Data model changes

None