form-select[multiple] should not display any indicator/icon

Created by: tkrotoff

Under Bootstrap 4 (4.6.0), custom-select[multiple] does not display the select indicator and the is-valid/invalid icon:

<select class="custom-select is-valid" multiple></select>

Under Bootstrap 5 (5.0.0-beta3), the new form-select[multiple] does display the select indicator and the is-valid/invalid icon:

<select class="form-select is-valid" multiple></select>

This is a regression.