[FIX] web: tab navigation with phone widgets in form view

This commit ensures that tab navigation works properly when editing a
form view that contains input fields with phone widgets. Previously,
pressing TAB would skip those fields.

addons/web/static/src/js/fields/basic_fields.js

@@ -966,7 +966,7 @@ var FieldPhone = FieldEmail.extend({
      * @override
      */
     getFocusableElement: function () {
-        if (this._canCall()) {
+        if (this.mode !== 'readonly' || this._canCall()) {
             return this._super.apply(this, arguments);
         }
         return $();