chore: use Deno 2.1 in tests

[vkarpov15]

Summary

We're using an out-of-date version of Deno, should test against latest

Examples

[hasezoey]

LGTM, though it seems deno now requires "implicit js" files to have package.json "type": "commonjs" as seen in the failing tests:

     info: Deno supports CommonJS modules in .cjs files, or when the closest
          package.json has a "type": "commonjs" option.
    hint: Rewrite this module to ESM,
          or change the file extension to .cjs,
          or add package.json next to the file with "type": "commonjs" option,
          or pass --unstable-detect-cjs flag to detect CommonJS when loading.
    docs: https://docs.deno.com/go/commonjs

This should be a non-breaking change as (at least in node) a absense of the type field should imply commonjs.

[vkarpov15]

We should be safe to add "type": "commonjs" because of Node docs here:

In the interest of caution, I'll move this back to 8.10.