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/package.json

@@ -1,25 +0,0 @@
-{
-  "name": "@n8n/client-oauth2",
-  "version": "0.1.0",
-  "scripts": {
-    "clean": "rimraf dist .turbo",
-    "dev": "pnpm watch",
-    "typecheck": "tsc",
-    "build": "tsc -p tsconfig.build.json",
-    "format": "prettier --write . --ignore-path ../../../.prettierignore",
-    "lint": "eslint --quiet .",
-    "lintfix": "eslint . --fix",
-    "watch": "tsc -p tsconfig.build.json --watch",
-    "test": "jest",
-    "test:dev": "jest --watch"
-  },
-  "main": "dist/index.js",
-  "module": "src/index.ts",
-  "types": "dist/index.d.ts",
-  "files": [
-    "dist/**/*"
-  ],
-  "dependencies": {
-    "axios": "^0.21.1"
-  }
-}