add_action( 'woocommerce_product_query', 'hide_products_in_shop' );

function hide_products_in_shop( $q ) {
    $tax_query = (array) $q->get( 'tax_query' );
    $tax_query[] = array(
           'taxonomy' => 'product_cat',
           'field' => 'slug',
           'terms' => array( 'uncategorized' ),
           'operator' => 'NOT IN'
    );
    $q->set( 'tax_query', $tax_query );
}