Delete legacy menu file

aleksis/apps/matrix/menus.py

-from django.utils.translation import gettext_lazy as _
-
-MENUS = {
-    "NAV_MENU_CORE": [
-        {
-            "name": _("Matrix"),
-            "url": "#",
-            "svg_icon": "simple-icons:matrix",
-            "root": True,
-            "validators": [
-                (
-                    "aleksis.core.util.predicates.permission_validator",
-                    "matrix.show_menu_rule",
-                ),
-            ],
-            "submenu": [
-                {
-                    "name": _("Groups and Rooms"),
-                    "url": "matrix_rooms",
-                    "svg_icon": "mdi:account-group-outline",
-                    "validators": [
-                        (
-                            "aleksis.core.util.predicates.permission_validator",
-                            "matrix.view_matrixrooms_rule",
-                        ),
-                    ],
-                },
-            ],
-        }
-    ]
-}