Update to v4 GitHub Actions checkout and upload-artifact since v3 is deprecated

[ia]

Hello. In short, "Actions" tab gives the following warning:

Deprecation notice: v1, v2, and v3 of the artifact actions
The following artifacts were uploaded using a version of actions/upload-artifact that is scheduled for deprecation: "blips-apple-universal.zip", "blips-linux-x86_64.zip", "blips-windows-x86_64.zip", "blisp-linux-aarch64.zip", "blisp-linux-armv7.zip", "blisp-linux-riscv64.zip".
Please update your workflow to use v4 of the artifact actions.
Learn more: https://github.blog/changelog/2024-04-16-deprecation-notice-v3-of-the-artifact-actions/

Therefore, this tiny patch switches GitHub Actions to the latest v4. I did enable Actions in my forked version of this repo, made builds, and checked the produced zips with this patch: the zips themselves and the content structured in the same way.

P.S. It's nice to see some familiar faces here :) The thing is that I may need to use this tool soon, so I decided to check "what's what" and how Pinecil v2 can be flashed, but I forgot that since it doesn't have DFU, this separate tool must be used. So, eventually I started to look around and see if I may be useful in any way around here as well. ;)