Bump lock-threads action to v5

[svlandeg]

Description

Update to v5 of https://github.com/dessant/lock-threads. Needed because the action was failing with

Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: dessant/lock-threads@v4. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.

Types of change

GH Actions fix

Checklist

• I confirm that I have the right to submit this contribution under the project's MIT license.
• I ran the tests, and all new and existing tests passed.
• My changes don't require a change to the documentation, or if they do, I've added all required information.