[FIX] web: do not open multiple groupBys submenus at once in pivot dropdowns

Introduced with odoo/odoo@5c5924af88

closes odoo/odoo#73076

Signed-off-by: Aaron Bohy (aab) <aab@odoo.com>

addons/web/static/src/legacy/js/views/pivot/pivot_renderer.js

@@ -92,8 +92,8 @@
             this.trigger('groupby-menu-selection', { fieldName, interval });
         }
 
-        _toggleMenu(groupNumber) {
-            this.openedSubMenus[groupNumber] = !this.openedSubMenus[groupNumber];
+        _toggleMenu(id) {
+            this.openedSubMenus[id] = !this.openedSubMenus[id];
             this.render();
         }
     }

addons/web/static/src/legacy/xml/pivot.xml

@@ -95,13 +95,13 @@
                 <t t-if="(item.fieldType === 'date') || (item.fieldType === 'datetime')">
                     <div role="menuitem" aria-haspopup="true" class="o_inline_dropdown">
                         <a href="#"
-                           t-on-click.prevent.stop="_toggleMenu(item.groupNumber)"
+                           t-on-click.prevent.stop="_toggleMenu(item.id)"
                            class="dropdown-item o_pivot_field_selection position-relative"
                            t-att-data-field="item.fieldName"
                         >
                             <t t-esc="item.description"/>
                         </a>
-                        <div class="dropdown-menu o_inline_dropdown" t-att-class="{ show: openedSubMenus[item.groupNumber] }" role="menu">
+                        <div class="dropdown-menu o_inline_dropdown" t-att-class="{ show: openedSubMenus[item.id] }" role="menu">
                             <t t-foreach="Object.values(intervalOptions)" t-as="option" t-key="option.id">
                                 <a role="menuitem"
                                     t-att-data-field="item.fieldName"