fix: Revert "Replace client-oauth2 with an in-repo package" (no-changelog) (#6265)

Revert "feat(core): Replace client-oauth2 with an in-repo package (#6056)"

This reverts commit 77ac953eaf.

packages/@n8n/client-oauth2/.eslintrc.js

@@ -1,14 +0,0 @@
-const { sharedOptions } = require('@n8n_io/eslint-config/shared');
-
-/**
- * @type {import('@types/eslint').ESLint.ConfigData}
- */
-module.exports = {
-	extends: ['@n8n_io/eslint-config/base'],
-
-	...sharedOptions(__dirname),
-
-	rules: {
-		'@typescript-eslint/consistent-type-imports': 'error',
-	},
-};