Update GitHub Workflows to remove redundant 'v' from release jobs

[sirosen]

This is a good, low-urgency item for anyone who wants to get involved with the project.

We transitioned from tags named X.Y.Z to vX.Y.Z, but the CI job for publication was setup to include a prefix v. It's a purely cosmetic defect in the build.
Example:

To fix, find the source of the errant extra v and remove it.

[webknjaz]

I think this got copied from my other workflows. Those use workflow_dispatch and so the input is unprefixed. If we ever get to changing the trigger, we'll need to get it back I suppose.