Add explicit `cache-dependency-path` to `action.yml`

[tianon]

This should squash the Warning: Restore cache failed: Dependencies file is not found in /home/runner/work/xxx/yyy. Supported file pattern: go.sum note we've been getting on all our builds. 🙃

[tianon]

Converting to Draft for now -- we need to test this commit/branch to make sure it actually works before we go ahead with it.

[tianon]

Run tianon/bashbrew@tianon
Run actions/setup-go@v5
  with:
    go-version-file: /home/runner/work/_actions/tianon/bashbrew/tianon/go.mod
    cache-dependency-path: /home/runner/work/_actions/tianon/bashbrew/tianon/go.sum
    check-latest: false
    token: ***
    cache: true
Setup go version spec 1.20
Found in cache @ /opt/hostedtoolcache/go/1.20.14/x64
Added go to the path
Successfully set up Go version 1.20
/opt/hostedtoolcache/go/1.20.14/x64/bin/go env GOMODCACHE
/opt/hostedtoolcache/go/1.20.14/x64/bin/go env GOCACHE
/home/runner/go/pkg/mod
/home/runner/.cache/go-build
Warning: Restore cache failed: Some specified paths were not resolved, unable to cache dependencies.

Nope! 🙃 (although this looks like a new warning, so maybe progress?)

[tianon]

So maybe we should cache: false instead? I don't know what that implies, more research required...