While I wouldn’t recommend it (not without changing the ‘previous’ visually because otherwise it could easily be confused with the submit-button), you could change the order by making the footer use CSS grids.
.gform_wrapper .gform_page_footer {
display: inline-grid;
grid-template-columns: 200px 120px auto; /* values to play with */
}
.gform_wrapper .gform_page_footer .button.gform_previous_button {
order: 2;
}