After removing ACF field groups from site, this function should be called once* on the fields that were trashed to remove them from WP Database.

removeACFDBMeta

<?php

/**
 * Remove ACF DB Meta
 *
 * After removing ACF field groups from site, this function should be called once* on the fields that were trashed to remove them from WP Database.
 * Removes them from the postmeta & options tables in the database.
 * Removes from all pages, posts, categories, taxonomies, users the field groups were attached too.
 * Note: Should only be called and used on local development, please remove from site when you deploy
 *
 * @version      1.0.0
 *
 * @param string/array $meta - Fields to remove from database
 * @param string $prefix - If fields need additional prefixing that was originally setup on fields & for repeater prefixes
 * @param string $table - DB Table to remove fields from(Note: fields are additionaly being removed from options table)
 * @param string $table_field - DB Column field name
 * @param string $table_value - DB Column field value
 *
 */
function removeACFDBMeta($meta, $prefix = false, $table = 'postmeta', $table_field = 'meta_key', $table_value = 'meta_value')
{

    global $wpdb;
    $prefixes = array();

    // If no meta fields
    if (empty($meta)) {
        print_r('No Meta Fields Specified');
        return;
    }

    // If array of meta fields
    if (is_array($meta)) {

        // Loop through meta fields
        foreach ($meta as $field => $value) {

            // Single meta field
            if (!is_array($value)) {

                // meta_key(prefix is repeater parent field with child fields)
                $meta_field  = $prefix ? $prefix . '_' . $value : $value;

                // Specified Table Removal
                $results = $wpdb->query("DELETE FROM {$wpdb->$table} WHERE {$table_field} REGEXP '{$meta_field}$'");

                // Options Table Removal(Remove if not needed)
                $option_results  = $wpdb->query("DELETE FROM $wpdb->options WHERE option_name REGEXP '{$meta_field}$'");
                $results        += $option_results ? $option_results : 0;

                // Print results
                print_r($meta_field . ' - ' . $results . ' rows removed in ' . $wpdb->$table . ' and ' . $wpdb->options); 
                echo '<br />';

            } else {

                // meta_key(prefix is repeater parent field with child fields)
                $meta_field  = $prefix ? $prefix . '_' . $field : $field;

                // Repeater meta field
                $max_repeater = $wpdb->get_var($wpdb->prepare("SELECT max({$table_value}) FROM {$wpdb->$table} WHERE {$table_field} = %s", $meta_field));

                // Remove repeater meta field
                removeACFDBMeta($meta_field, false, $table, $table_field, $table_value);

                if (!empty($max_repeater)) {

                    // Meta field repeater loop
                    for ($i = 0; $i < $max_repeater; $i++) {
                        $meta_field = $prefix ? $prefix . '_' . $field . '_' . $i : $field . '_' . $i;
                        removeACFDBMeta($value, $meta_field, $table, $table_field, $table_value);
                    }
                }
            }
        }
    } else {

        // meta_key(prefix is repeater parent field with child fields)
        $meta_field = $prefix ? $prefix . '_' . $meta : $meta;

        // Specified Table Removal
        $results = $wpdb->query("DELETE FROM {$wpdb->$table} WHERE {$table_field} REGEXP '{$meta_field}$'");

        // Options Table Removal(Remove if not needed)
        $option_results  = $wpdb->query("DELETE FROM $wpdb->options WHERE option_name REGEXP '{$meta_field}$'");
        $results        += $option_results ? $option_results : 0;

        // Print results
        print_r($meta_field . ' - ' . $results . ' rows removed in ' . $wpdb->$table . ' and ' . $wpdb->options); 
        echo '<br />';
    }
}

/**
 * One Time Function Call, below is fields, and field repeater
 * Note: Should only be called and used on local development, please remove from site when you deploy
 */
removeACFDBMeta(array(
    'dl_link_type',
    'dl_section_title',
    'dl_array' => array(
        'dl_school_name',
        'dl_school_url',
        'dl_school_description'
    ),
    'addl_content'
));


/**
 * One Time Function Call, below is a single field
 * Note: Should only be called and used on local development, please remove from site when you deploy
 */
removeACFDBMeta('dl_link_type');