[IMP] web: document position possible value

Position option has only 4 possibles values.

closes odoo/odoo#105271

Signed-off-by: Samuel Degueldre <sad@odoo.com>

addons/web/static/src/core/popover/popover_hook.js

@@ -27,7 +27,7 @@ export function usePopover() {
          * @param {function()}              [options.onClose]
          * @param {function()}              [options.preventClose]
          * @param {string}                  [options.popoverClass]
-         * @param {string}                  [options.position]
+         * @param {("top"|"bottom"|"left"|"right")}   [options.position]
          * @returns {function()}
          */
         add(target, Component, props, options = {}) {