dev-cmd/typecheck: fix Ruby version conflict in sigil bump

[p-linnane]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
• Have you successfully run brew lgtm (style, typechecking and tests) with your changes locally?

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When running brew typecheck --update --suggest-typed, spoom's exec method uses Bundler.with_unbundled_env which strips environment variables that ensure Homebrew's portable Ruby is used. This caused #!/usr/bin/env ruby in the srb wrapper script to resolve to the system Ruby 2.6 on macOS GitHub runners.

Lets use the native sorbet binary from sorbet-static directly instead.

Seen in https://github.com/Homebrew/brew/actions/runs/20927488069/job/60129300539:

==> Checking if we can bump Sorbet `typed` sigils...
Checking files...
/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/bundler/lockfile_parser.rb:108:in warn_for_outdated_bundler_version': You must use Bundler 2 or greater with this lockfile. (Bundler::LockfileError)

[MikeMcQuaid]

Makes sense, thanks!

[p-linnane]

Hmmm. This might not be complete. Let me debug more.

https://github.com/Homebrew/brew/actions/runs/20927880452/job/60130701821

EDIT: The issue is that the Sorbet workflow isn't really designed for testing changes. That was a misunderstanding on my part. This works as intended.