Modernize eslint.config.mjs. NFC (#23385)

Author: sbc100

.circleci/config.yml

@@ -6,7 +6,7 @@ orbs:
 executors:
   linux-node:
     docker:
-      - image: cimg/node:18.20.3
+      - image: cimg/node:20.15.1
   linux-python:
     docker:
       - image: cimg/python:3.10.7

eslint.config.mjs

@@ -1,13 +1,9 @@
 import globals from 'globals';
-import path from 'node:path';
-import { fileURLToPath } from 'node:url';
 import js from '@eslint/js';
 import { FlatCompat } from '@eslint/eslintrc';
 
-const __filename = fileURLToPath(import.meta.url);
-const __dirname = path.dirname(__filename);
 const compat = new FlatCompat({
-  baseDirectory: __dirname,
+  baseDirectory: import.meta.dirname,
   recommendedConfig: js.configs.recommended,
   allConfig: js.configs.all
 });