cmd/tap-info: revert exit code changes to --json only

[Bo98]

#21310 presented a good case for returning an exit code on brew tap-info however this shouldn't apply to --json for multiple reasons:

• Unlike regular brew tap-info, brew tap-info --json is designed to work on uninstalled core taps (i.e. from the API).
• brew tap-info --json is able to provide install locations even when taps aren't installed.
• There's already a dedicated entry for installed in the JSON
• Being able to differentiate between parseable JSON output and non-parseable output (e.g. Ruby error) is important.

This fixes regressions seen downstream (public example: rcmdnk/homebrew-file#373).

The case originally presented in #21301 is still retained since that talked about the non-JSON case.

[Copilot]

Pull request overview

This PR reverts exit code behavior changes for the --json mode of brew tap-info, addressing regressions in downstream tools. The JSON mode now always returns a success exit code (0) regardless of tap installation status, while the non-JSON mode continues to return a failure exit code (1) for uninstalled taps.

• Removes Homebrew.failed = true check from print_tap_json method
• Simplifies the JSON generation code from explicit iteration to a concise map(&:to_hash) call
• Maintains existing behavior for non-JSON mode where uninstalled taps trigger failure exit codes

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[MikeMcQuaid]

Makes sense for JSON case, agreed, thanks!