v2: Don't install CUDA by default (and upgrade to latest Cog)

[zeke]

This PR includes two breaking changes which I want to roll out in a new major version v2:

1. Changes the install_cuda input to default to false. Most models don't need CUDA at build time. Workflows are much faster without it.
2. Changes the default version of Cog installed by the Action from 0.8.6 to 0.9.7

Resolves #31

cc @luismavs and @nateraw who originally had the bright idea to make CUDA optional: #13

[zeke]

Smoke testing this here: https://github.com/zeke/hello-world-cog/actions/runs/9120284202

If it succeeds I'm going to do this:

git checkout main
git fetch --all --tags
git tag v2.0.0
git tag v2 --force
git push --tags --force

[zeke]

Smoke test passed!