Investigate if manual notarization is still needed

[nikku]

What should we do?

We currently manually notarize builds of the app for MacOS. To me it appears like this is supported by electron builder.

Tasks

• Perform notarization through electron-builder
  • Adjust secrets to enable it
  • Migrate secrets to vault in the process (https://github.com/bpmn-io/internal-docs/issues/802)

Why should we do it?

This will allow us to drop the direct notarization dependency and use what is provided and tested in the builder.

[nikku]

Tagging as spring cleaning, maybe we also tackle this as part of #4588.