Make Experience field Optional

functions.php

// Add your own function to filter the fields
add_filter( 'submit_resume_form_fields', 'custom_submit_resume_form_fields' );

// This is your function which takes the fields, modifies them, and returns them
function custom_submit_resume_form_fields( $fields ) {

    // Here we target Candidate Experience and make it Optional.
    $fields['resume_fields']['candidate_experience']['required'] = false;

    // And return the modified fields
    return $fields;
}