build: remove release on pull-request

[PsypherPunk]

Mostly a suggestion at this point: Actions are currently failing due to the default dev tag being invalid for some parts of the release workflow.

However, that raises the question as to whether it's appropriate to run a release workflow for a pull-request. I'm suggesting not herein and instead suggesting that this workflow is run only when explicitly tagged and the build workflow should be relied on for testing, etc.