Replace lockbot with GitHub Action

### 🤔 What's the problem you're trying to solve?

LockBot has been deprecated and replaced with a GitHub Action named [lock-threads](https://github.com/dessant/lock-threads).

### ✨ What's your proposed solution?

Convert the projects with a `lock.yml` to the GitHub Action.

### ⛏ Have you considered any alternatives or workarounds?

Remove the `lock.yml`, we haven't really used it much.