Tagging suggestion: have v4 always point to the latest v4.x.y tag

[mdickinson]

I ran into an issue yesterday because I was expecting uses: enthought/setup-edm-action@v4 to automatically pick up the latest v4 version of the action. It turned out that I had to specify @v4.1 explicitly to get the 4.1 version.

It looks as though what "official" actions like checkout do is to tag releases with v4.minor.micro and then recreate the v4 tag every time there's a release to point to the latest release: https://github.com/actions/checkout/tags. We could do the same here.

(It would probably make sense to have v4 be a lightweight tag rather than an annotated tag, but to use annotated tags for the releases as normal.)

[mdickinson]

It's also worth noting that GitHub's dependabot doesn't seem to recognised that v4.1 is an upgrade to v4, so doesn't suggest updating.

See e.g. this PR that dependabot created yesterday, where it proposed updating v2 to v4 (rather than the expected v4.1): enthought/pyface#1270