Automated Testing CI Docs for Edge Functions dont include setup deno step

[Ben-Vollrath]

Improve documentation

Link

https://supabase.com/docs/guides/deployment/ci/testing

Describe the problem

In the docs guides about Automated Testing for Edge Functions, no setup deno step is included. Deno test command will fail.

Describe the improvement

Add a denoland setup step to the example workflow so it succeeds.

      - uses: denoland/setup-deno@v2
        with:
          deno-version: latest

[Ben-Vollrath]

I did a PR to resolve this docs issue: #320