Replace actions/setup-go with actions/setup-python in smoke test

[jeffwidman]

The smoke test fixture (.github/workflows/i-am-a-smoke-test.yml) previously used actions/setup-go, which is also used in real CI workflows (smoke.yml, cache-all.yml, etc.). This caused Dependabot to open PRs like #160 that conflicted with the smoke test's intentionally-pinned version.

At the time, we ignored them:

• Bump actions/setup-go from 4.1.0 to 5.0.0 #160 (comment)

However, that's now a problem because the latest version of actions/setup-go has a caching update that would be nice to have:

• https://github.com/actions/setup-go/releases/tag/v6.3.0

So I've unignored that dependency:

• Bump actions/setup-go from 4.1.0 to 5.0.0 #160 (comment)

However, this will try to update our test workflow, which we do not want.

So instead, let's:

• Replaces actions/setup-go with actions/setup-python in the smoke test fixture, since actions/setup-python isn't used in any real workflow
• Regenerates the smoke-actions test
• Adds explicit ignore rules in dependabot.yml for all three test fixture actions (actions/setup-python, actions/setup-ruby, actions/setup-node) to prevent Dependabot from proposing updates to intentionally-pinned dependencies

[jeffwidman]

I'm not sure if I can actually do this... will the dependabot test command look for this dependabot.yml file and read these ignores and skip it?

[jeffwidman]

It looks like this doesn't break dependabot test, and it's certainly helpful to prevent PR's from showing up that would break our tests.

It also provides a clear documentation link within this file if someone is like "why are these not getting updated?"... it'll show them "oh, they're used int eh tests, so we tell Dependabot not to actually open PR's to bump them"

[jeffwidman]

I'm not too familiar with the format of the output so I'm a little confused to see the actions/setup-go still in here... perhaps that's not expected / desired and we'll need to regenerate this file after bumping the non-test-fixture references to actions/setup-go to the latest?

• Bump actions/setup-go from 4.1.0 to 6.3.0 #410

[kbukum1]

LGTM