fix: don't use optional chaining operator (#2078)

Author: vursen

.eslintrc.json

@@ -6,7 +6,7 @@
   "parser": "@typescript-eslint/parser",
   "parserOptions": {
     "sourceType": "module",
-    "ecmaVersion": 2020
+    "ecmaVersion": 2019
   },
   "plugins": [
     "prettier",

packages/vaadin-grid/src/vaadin-grid-filter-column.js

@@ -57,7 +57,7 @@ class GridFilterColumnElement extends GridColumnElement {
    */
   _defaultHeaderRenderer(root, _column) {
     let filter = root.firstElementChild;
-    let textField = filter?.firstElementChild;
+    let textField = filter ? filter.firstElementChild : undefined;
 
     if (!filter) {
       filter = document.createElement('vaadin-grid-filter');